It's probably worse if it was once reliable and now not, compared to if it's never reliable: if it's never reliable, you've been trained to have a huge safety margin and backup plans, if it's reliable and suddenly it messes up, you're thrown in a new situation and have to think "Shit, what do I do now?". Probably very stressful, and it leads people to avoid the service altogether.

Although apparently NYC subways used to be better too.