But RU is a private school game. Played largely by middle/upper class people, it's part of their culture. You seem to be overlooking this cultural tie. It's part of who they are, just as RL is a working class Northern game popular in coal mining towns. You can't detach sport and culture. Do private schools favour RU? Of course they do, because it's embedded in their cultural identity, just as Irish schools favour Gaelic football.
Private schools also make up a tiny percentage of schools, what about the public/state schools? Huge swathes of England are working class, yet you constantly target a small demographic group.
RL has largely been rooted in northern English towns because that's where the cultural ties are. The hub of coal mining towns, and in those towns one generation passes on their interest to the next one. RU doesn't get a sniff in these towns because there isn't any cultural link to it.
Both sports are niche, and as I said collision based sports have always had much lower participation levels. The two main RL playing nations are England and Australia;
Ranked the 27th most popular participation sport in England, there are 44 thousand RL players aged 16 and over.
http://www.telegraph.co.uk/sport/2017/02/15/popular-sport-england/rugby-league/
In Australia, Aussie Rules is the 12th most popular participation sport, and the highest ranked collision sport. RL is 15th. RU isn't in the top 20.
http://www.roymorgan.com/findings/6...hildren-and-adults-december-2014-201503182151
A 2016 study has RL as the 9th most popular club sport in Aus with 247 thousand participants. RU doesn't appear at all in the list.
https://thenewdaily.com.au/sport/football/2016/12/08/most-popular-sport-in-australia/
Collision based sports have always been niche outside their cultural heartland. RU, RL, Aussie Rules, American football, Gaelic football etc etc. What you want for RL - becoming massive - is not realistic. For all its middle class wealth RU has barely any presence outside of England and its British commonwealth outposts. 97% of the 33 million audience for the 2011 RUWC final came from the British isles, Australia, NZ, South Africa and France.
http://www.nzherald.co.nz/sport/news/article.cfm?c_id=4&objectid=10761073