I'm not saying it always happens, I'm saying it can happen. I've experienced it with both public and private games. Maybe you've been lucky and it's never happened to you. Congratulations! You've been lucky! But it does happen.Play that occurs at Conventions, or other Public Tables, be it AL, the RPGA, or other similar entities is a fringe element of the limited slice of persons that play Roleplaying games.
Perhaps, something in the structure of Public Games facilitates disruptive play.
Perhaps, something in the structure of Private Games, dissuades disruptive play.
I assign very little probative value to personal anecdotes about A-holes on Discord Severs, or A-holes in AL, or A-holes in Living FR or Greyhawk.
Most games of D&D, past and present, are not public. Most participants in RPG games, past and present, were not involved in public games.
Crying out "What about Adventure League Games?!" is like the cry of
"What about the children?!" from the great satanism/suicide outcry of the 1980s.
It seemingly leads to proposing overreaching and authoritarian policies, in response to issues that are not well understood, and is 'fixing' a problem, most games, don't have.
Therefore my advice for DMs boils down to:
Try to make the game fun for everyone including yourself. Listen to people but don't have long discussions about the rules at the table during the game, make a ruling and if there's a longer discussion do it after the game. Don't be afraid to tell people that you simply need to think about it and remember that sometimes there is no way to please everyone, sometimes there is no "right" answer. While you can and should listen to your players, as a DM you make the final call.
See also the PHB and DMG on the role of the DM. Feel free to disagree with my advice. But saying that it doesn't happen? Ignorance may be bliss but it's still ignorance.