I just had a look at commuting times on Google Maps.
Hurstville to SFS is 48 min.
Manly to SFS is 1hr 12 min.
Cronulla to SFS 1hr 33 min.
Canterbury to SFS in 54 min.
Campbelltown to SFS in 1 hr 30 min.
North Sydney to SFS in 36 min.
Penrith to SFS in 2hr 21 min.
Parramatta to SFS in 1 hr 8 min.
So why aren't more teams based out of the SFS?
Manly, Roosters, Souths, Cronulla and St George could use the SFS as their home ground and their fans can get to games faster than a person travelling from Redcliffe to Lang Park, which takes 2 hr 6 min according to Google Maps.