This is interesting I did a bit of Googling, I guess it varies by sport quite a bit.
https://www.post-gazette.com/sports/around-the-league-nfl/20...
Some sports, most coaches came from players, but the NFL notably does not.
Some sports, most coaches came from players, but the NFL notably does not.
I can't think of any sport where players are expected to become coaches.
In amateur sports it's common. E.g. in rowing, cycling, fencing, cross country skiing, etc., people are generally expected to coach at some point. Albeit usually while they're doing the sport, and not necessarily as their primary careers.
This does, however, not necessarily mean that everyone is a good coach, nor does it mean that everyone should stop practicing what they're doing and focus solely on coaching.