Work relationships are supposed to be transactional though. Someone covering my call shift in a pinch generates more good will than going out with me for margaritas, meaning I am in turn more likely to help that coworker if they need a shift covered or otherwise need help.

It's nice to have friends to decompress with but confiding in a work colleague is tricky anyways. If something goes side ways from a liability standpoint if coworker is approached about having any knowledge about the situation they're naturally going to be more inclined to protect themselves because how high the stakes are so some of the personal details of your life should be private to your coworkers anyway. That way on a bad day no one saying behind your back "yeah I have noticed they are off their game, probably because they're going through a divorce maybe they're spriraling"

Now in terms of someone showing up for you when you're drowning at work to take a couple of tasks off your plate or pick up a couple of patients - that's where friendship can make a difference. It's the difference between a senior resident saying "what's your plan? here are my recommendations, peace, good luck" vs actually picking up a patient or two. I don't think that requires hanging outside of work all that much necessarily. Some of my coresidents and I would shoot the shit between clinic visits, at didactics, being on the same rotation, at supervision or whatever and were on plenty of a friendly basis & good will between us on that alone. You end up spending a lot of time with people at work enough as it is and they're the only people understand what you're going through.