Who determines what anyone deserves? Sure RM could pay more, but (as I've said) that could easily lead to fewer jobs in RM. Those people then end up on benefits, or working for even less money elsewhere.
As I say, I don't like it, but (rightly or wrongly) we live in a free market economy, and that is the sort of thing that happens.
Other current strikers are not quite in the same situation. Nurses, border force, railway workers; irrespective of what they might or might not deserve they don't work in a competitive market, so their strikes are more likely to work, and be less likely to damage their own employers' long term "business".