We differ. It has grown because of this very reason. Without the Sydney clubs: it's not attractive at all. Just ask why the Broncos, Canberra, Knights etc wanted in. They all wanted to be part of this much reveared and envied competition sprouting from Australia's largest city.
I know why the Raiders joined (the Broncos joined for very similar reasons as well), and it's not particularly because they wanted to play against the Sydney clubs because playing against the Sydney clubs offered them any real advantages, it's quite a bit more complex then that.
In the 60s and 70s RL in Canberra and the surrounding regions was stagnating because prior to those times it could compete with the Sydney clubs for players and exposure in the local region.
Prior to the 60s and 70s the NSWRL wasn't on tv so the only way you could follow it was listening to it on the radio or reading the results in the paper (which many did btw), but while it was on the radio big local games were often on the radio also and not only could you read the local results in the paper you could attend the local teams games, which was what most did. Most peoples first team was the local team but they loosely followed a Sydney team as well. What started to happen in the 60s was the NSWRL started to be broadcast regularly so now you could watch NSWRFL games on tv as well which gave them massive exposure that the local clubs couldn't compete with, but what really started to impact the local comps and teams was the NSWRL clubs started to be a real option for local players.
Prior to the the 60s and 70s there were players that would come through a club and play their whole careers at that club that were local stars so to speak. To no small degree those local stars pushed the growth of the sport in the region, going to see certain players was a big draw card to get people through the gate which then funded further growth of the sport in the region, and those players had an even bigger impact on getting kids interested in the sport and keeping them interested. Once the 60s and 70s came along and the NSWRL was getting more exposure the Sydney clubs didn't have only a little more money to offer a local player to convince them to move like they once had, they suddenly had a lot more money to offer and the glamour of potentially being on tv and the celebrity that came with that, so while before hand maybe one or two local star players in a whole generation of players would try their luck in Sydney now almost every star player was being recruited by Sydney clubs, at which point the main draw card to get locals throw the gate at local clubs had been eaten up by the richer Sydney clubs that could offer the players better opportunities, so suddenly the local leagues were a lot poorer cause they couldn't attract as many people through the gate as they once could, but the real impact was that suddenly getting kids to be interested in the sport and start playing it became a whole lot harder cause one of the main things that was drawing them in was suddenly gone, so suddenly not only were the local clubs a whole lot poorer their juniors had halved (or more) and they weren't producing as many players to replace the local stars as they could in the past, which really impacted them.
Now where this really hurt Canberra in particular was that the ACT had a representative RU team, so while all the local RL star players were being eaten up by the Sydney clubs to mostly never to be heard of again the RU stars were also being eaten up by Sydney clubs but many of them would come back semi-regularly to play rep games against this or that team, and Canberra had (and still has) a strong private school culture that churned out local RU players of a high standard to replace the lost local stars at a rate that RL simply couldn't compete with at the time. So what started to happen in the 60s and really came to a head in the 70s was that where before hand Canberra and the surrounding regions were pretty evenly spilt market where RU, Aussie Rules, and RL had equal shares suddenly RU had a bunch of advantages and was relatively quickly murdering everybody else (except soccer, but there was a whole other set of unrelated dynamics and variables that went into soccer dodging that bullet).
In the mid to late 70s the Queanbeyan Blues (among others in both RL and Aussie Rules) realised that if they didn't find a way to get RL a heap more exposure and a huge cash boost locally that RL was going to be eclipsed by RU in a generation or two, cause it was all well and good that every man and his dog had a Sydney club that they followed, but almost none of them played RL or really supported a local club anymore but all of them played and support RU. The only way that they could figure to compete with RU was to create an entity that could compete with the NSWRL clubs for players and exposure locally and to do that the best way they figured was to create some sort of unified entity that played in the NSWRL, then one thing lead to another and as an end result you have the Raiders.
If the Raiders didn't come into being when they did then not only would RL have struggled to identify local talent early to compete with RU that had that capability locally, the money wouldn't have been in the sport locally to compete with the money on offer in RU, so at least Ricky Stuart, Glenn Lazarus, Bradley Clyde, and quite a few others in that first generation of great Raiders players would have almost certainly followed David Campese's lead and pursued RU instead of going with league, and each generation after that generation more and more would have gone Unions way following their predecessors lead, which would have had a further compounding effect on the sport locally.
So yeah, the long and short of it is the Raiders (and the multiple attempts to join the VFL/AFL by Canberra clubs) exist largely because of the growth that RU saw locally as a result of the growth that the NSWRL and VFL saw nationally, however they didn't join the NSWRL cause they wanted to play the Sydney clubs for some nebulous reasons but because they not only wanted but needed to be able to offer players the same opportunities locally that the NSWRL clubs could offer in Sydney if the sport wasn't going to continue to stagnate and then start dying in the region.
BTW, I apologise for the really long and dense post, but it is a relatively complex subject that requires detail (by an internet forums standards) to properly explain.
