for comp it is because you can't actually evaluate how good players are without limiting their games

The logical (and right) answer is so that someone with no life plays hundreds of games throughout the week. It would be unfair to people who have jobs and responsibilities that can't play dozens of games a day.

For comp 5 is a manageable amount a day.

It's to force you to make a 2nd account.

If you want to play more than what's allowed then u have a problem

actually it's to ring-fence the much acclaimed Highest total score! section of the HoF (hall of fame) - we don't want any old player making it onto there!!

So you don't aimlessly play thousands of games of mafia over the span of weeks to make up for your lack of life, OP.