I’m a baseball coach and there are plenty of times when I shower with my players. When I played in college, the coaches usually showered with the players, it just depended on the type of facility. Some places had separate showers/changing areas for coaches, but most do not for baseball.
Sometimes even for football, there may be another changing area for coaches but it was usually small so some of the coaches would go shower in the player area just to speed things up and not have to wait.
I don’t usually shower with random students, but I wouldn’t be opposed to it I guess. Where I coach, I work our in the school fitness center and weightlifting area and shower there and only the student-athletes use that area so only the players I coach shower with me there.
It was the same way with the coaches when I played in college.