Sunbury already has a line - upgrading it is thus cost effective.
Building a massive new line to a dead growth area is not cost effective.
Your taxes pay for a transport service, not a train.
You want a rail line? Don't move to Rowville.
It would be nice for a line to Rowville but how many billions of dollars needs to be spent to service 40,000 people
Sunbury and melton both had regional fast rail then sunbury got electrification both paid for mostly by eastern suburbs taxpaiers that actually work n pay for life in the western suburbs so thats 2 big projects and nothing for rowville