Strong unions such as ASLEF and RMT have an awful lot to do with it. Also how many train drivers do the job for nothing just to gain experience plus the dreadful Pay 2 Fly schemes that were/are in operation in the aviation world. Train drivers don't trample over each other to get onto the "flight deck" either.
Totally agree. We as a group do not do ourselves any favours, particularly here in the UK.