I think that consulting with peers (whether it is called supervision or something else) is highly beneficial in every profession, even in those that do not involve dealing with people. It's not only for reality checks but also to help keep up with the developments of a field that one person perhaps will not discover. However, it is only useful if it is quality consulting/supervision and not just a means of getting validation from and venting with another individual.

I am not a clinician/therapist but have worked with many in my job and often participate in clinically-oriented meetings, conference sessions etc with Ts and psychiatrists. To be honest, I am too often surprised (and also kinda grossed out) at how much client detail they sometimes present openly in forums like that. Also how (usually the same people who do the TMI) they often focus completely on the client in a case discussion and don't integrate what they do, don't question what they do - an alarming lack of introspection. The pattern often tends to be that those individuals go into unnecessary details of their experience with a client in a way that presents the clients as quite disturbed and flatters the skills of the clinician. Of course it is not everyone but, at least in the forums I go to, I encounter it with a frequency that seems alarming to me as an outsider (non-clinician, ex therapy client). So imagine if a person with that lack of introspection and responsibility teaches/supervises students... luckily the students usually have multiple mentors throughout their training. Of course this is not a special characteristic of mental health clinicians but a general feature that is present in every profession - there are bad teachers, supervisors, practitioners everywhere. Why, IMO, it is so important to receive mentoring and consult with a variety of peers instead of only one and the same one for years. Not sure how most Ts handle this in their private sphere, whether they use different supervisors or stick with one? I guess depends on the T. If I were a T dealing with many different client issues, I would probably try to consult with separate experts in the different issues/fields instead of just one person that I happen to like and click with.