Is it a dead stat for the sake of having stats - or does attendance actually do something? Can we expand stadium? Do we get more money?

I think higher attendance gives you more money to sign coaching staff

Attendance is primarily window dressing, it has little impact on the game. The only impact is how much crowd noise affects the opposing team. The calculation is based on % filled.

At one point it impacted the coaching staff budget, but that was removed a long time ago as I felt it just made it harder to improve bad teams.