Fundamentally, you can't have your cake and eat it. The job security of being in the public sector (as the franchised TOCs have been, at least since the pandemic) comes with caveats - most notably, significant pay restraint when government finances are tight. You don't exactly see civil servants getting pay increases at the moment.
Sadly, a lot of people have unrealistic expectations from previous generous pay deals when the industry was in a better financial position, and when it was not under the current level of scrutiny by the government.
It's telling how the Scottish Government hasn't felt any pressure to agree to the RMT's demands, despite more than 7 months of industrial action. That should be a rather large clue as to where this is heading.