How much customer service should a $0/month subscription buy?
Without any revenue they close up.
How many customers can they afford to lose? 5%,10%, 90%
If they don't support the free tier users they will lose them. At one point vimeo was making a serious run for global marketshare.. now it looks like they are in a different market..
Vimeo hasn't been going for global marketshare of video watching in well over a decade - it ceded that competition to YouTube very early on by policing content more actively (Viacom sued YouTube in 2007 for $1B because of its lax enforcement of rules).
Vimeo chose a different direction, launching a paid account in 2008: https://vimeo.com/1977937