They have very little power in most primary care specialties. The expectation from hospitals is you will work this hard or they won’t hire you. Hospitals are more than happy to just dump more hours onto their over-exhausted doctors rather than hire new ones who ask for fewer hours. The expectation from other doctors is you will work this hard because if you don’t, someone else will have to pick up the slack. Also, most of them sign as part of their contract basically “I’ll show up outside of contracted time if it is necessary for patient safety”, turns out this is like 50% of the time because they’re so understaffed
Doctors have invested huge sums of time, money, and effort into getting the qualifications needed to perform their jobs, and there are few alternative jobs they can transition into if they are given a bad deal.
If you don't even know about these organisations then you're not really qualified to talk about what doctors should or shouldn't be doing or what power they do or don't have.
How do you know they haven't? Just because things aren't perfect doesn't mean things can't be better than they were previously, the NHS has been around for 70 years after all.