I have it turned on even though I’m reasonably young and active. I live alone and occasionally get on ladders to do work or do other things that could wind up with me falling and hurting myself, so I feel like it’s at least a bit of extra protection if something were to happen. I’ve had a few false alarms, but really very few, and assuming that you are in fact still conscious and not badly injured the worst is that you need to do is acknowledge to the watch that you are OK and it won’t call 911.
Obviously the OP’s situation where he set his watch on the counter and then left it to take a shower was a bit different, but I feel like in most situations the worst you’ll have to deal with is acknowledging a false alarm, not paramedics beating down your door. There are certainly times when false alarms could be super annoying to deal with, such as if you‘re wearing winter gloves while skiing or work gloves while working, but in my case, at least, I don’t think I’ve had more than 2 or 3 false alarms in the two or three years this feature has been available.
If you haven’t even tried the feature because you’re afraid of false alarms then I think it’s worth trying. You‘ll probably find that there aren’t very many. And if you do get a lot because of specific activities that you do then by all means turn it off again.