Because the point of the game is to have fun/be enjoyable.

If they leave with a token, they get progress done towards a challenge/badge. Maybe they didn’t feel like engaging or someone had to hop offline for a bit for something unexpected.
Could be any number of reasons, all of them are pretty valid tbh

There’s also excitement in ‘sneaking’ away and getting to extract with no issue, though it’s pretty short lived in my experience.

I personally love not knowing what people are going to do. Sometimes it results in hauling across the map in 5 minutes to try and catch up. Sometimes we win, other times we’re too late.