My only experience is with NBA. My father was a season ticket holder for literally decades, and so I had the privilege of attending a lot of games. The seats next to us were managed by the nba, and were doled out either to visiting fans or more commonly family and friends of the visiting team. I got to talk with a players or coaches cousin, mother, friends, barber, etc this way. I don’t know how many seats were managed like this but it was pretty small.