I am not convinced. I agree the current model for most higher education of 3 years with only lectures, then the rest of your career with only "on the job" training is not optimal, but you already noted that is not how medical degrees work, so why should others have to? The hard line between 3 year academic degree and "vocational" training does not make much sense and could be blurred to everyone benefit.
Plenty of other jobs carry a lot of responsibility. The life or death aspect is particularly obvious with civil engineering and software development for medical devices, but if you compare the impact of those
fujitsu programmers that made the post office system does it make sense to say they have not held other peoples lives in their hands, and failed?
As someone who works in software development, training can only get you so far. Most of the issues companies experience arise out of management issues, scheduling issues, project commitment issues, failing to tackle technical debt, etc. These ultimately (to be rather reductive) stem from the need to make money. It's hard to justify a month working out technical debt if you need to deliver to three customers (let's say) in that time. Given a choice between "earning money" and "fixing old stuff that can be covered up until it's too late", it seems that companies overwhelmingly vote for the former. I don't see this as something degrees can improve, realistically.
Other jobs definitely carry similar responsibility. I'm just suggesting that because doctors literally hold patients' lives in their actual hands, the training requirements are therefore stricter. Management issues can of course compound problems in any profession, but there is a hands-on aspect to a lot of a doctor's work that carries significant weight. Does this mean I think something like, say, tractor driving
shouldn't come with strict training? Of course not. But again, that's not degree territory either. It's a complex topic that kinda covers education as a whole (which is obviously going to be very country-specific).
Ultimately, I can't answer why other degrees aren't as stringent as medical degrees. I would imagine because staffing and training is hard enough as it is, for other subjects, and this would price some degrees out of affordability in terms of both university-side recruitment, and student loans (don't get me started on that mess). The necessity of medical degrees creates their existence, would be my "tl;dr". Other professions can get away with less (though I'm sure there are some professions that are somewhat comparable - I think law could be a good example, though degree requirements are often "soft" requirements in that you're not going to
get the job unless you do the prerequisites, whereas in medicine the prerequisites are baked into a course by default, making it longer by default).