It's not mandatory but when you've got points on the line they probably didn't want to be seen to be making decisions that could cost midfield teams a chance at points, even if that meant an extra lap or two behind the safety car.
Drusenija
Agree on the GDPA role, but they did explicitly ask him about it during the interview so figured it was at least worth mentioning.
Best theory I have is all the teams are expecting some sort of sanction over the incident and they all want to be able to be arms length and say "that was the FIA's decision" and not have sound bites where they were suggesting that something should happen.
All the drivers clearly have been advised by their teams to not comment on the Max situation. Oscar basically said "didn't have context on what happened, only saw they collided, can't comment", Lando ignored the question entirely and just started talking about his own race, George was pretty non committal despite being involved in the incident and also flat out refused to comment in his role as a GPDA director (says he was "too close to comment").
Clearly they don't want any sound bites out there about it.
Now we just need Ferrari to do a partnership with Nintendo and we can literally have Mario vs Sonic on the F1 track.