If there is a slow driver in front of me who
a) has a bad connection = lag + warps
b) drives like a madman (no pun intended )
c) lots of slow traffic in front of you, maybe some lapped people too
In these cases it is strategically wiser to take the pitstop, because there is no good racing in front of you. These events are defenately rare events, so these are more of positive sides what a mandatory pitstop can do. One thing that is a better point is that mandatory pitstop allows more room for errors. You can overcook your tires or even damage your car and fix it without losing too much time, because everyone else has to make a pitstop too.
It depends two equal things. One id defenately the player amount and the other is the track length. On Nürburgring we could have 100 cars and no one would see anyone else, or we could have 8 people on So1 with MRT and it could be a tigh fight.
All in all, I think the 5 lapper has become a norm, and as such most races are set to 5 laps even if the majority wants slightly longer races. Everytime I get my hands on some server, I set the total laps nearer to 10 than 5. 5 laps are just too short on most combos.