The government is not going to spend money on a stadium for one club, with little commitment to the area/site. Penrith are established at Mulgoa Road, with their Leagues Palace directly across the road.
There's also this philosophy of building/moving to a growth area, and not a central area accessible by existing supporters. Western Suburbs/Balmain, and newer Wests Tigers fans are all over the metropolitan. Unfortunately it's tough to do an accurate member analysis of where the supporters are concentrated, because the membership data is skint. But you're asking the government to invest millions on a project for an organisation (and ownership organisation) who have a tendency to flip-flop, fark up, and continuously move their region of focus, and a history of in-fighting and pulling in different directions.
It's shit to say, but Parramatta is the future. There's an existing stadium, a very good stadium, a beautiful stadium, in the middle of the metropolitan, and accessed by numerous transport options, lots of transport, new and existing transport. Just don't visit Parramatta Leagues.