@questingbeast Technically, I am not in the midst of an American PhD, but a Canadian one. I'm pretty sure they're fairly similar though, so imma go ahead and respond to you.
Yes, you're right! Universities DO like money. so much! But also, we have a lot of other tasks we need to perform, that go way beyond learning a second language (by the way, that part's not that hard... all i had to do was pass a super easy reading comprehension test). I assume you're a UK or EU scholar? I did my MA in London... and dude, it was substantially more lax over there. oh, how I wish I had stayed! In these here parts, we have all sorts of hoops to jump through. Two very large ones: the field exams that need to be passed. Oh lord, those are frightening and the reading lists for them are unwieldy. Like those scrolls in comedic movies that keep on rolling and rolling. We also have coursework, believe it or not. At my uni, we need 18 credits to qualify; most try and get this out of the way in the first few years. It's basically like another MA program tucked inside of your PhD one. Fun, right? I also had to spend like, a year developing my diss-proposal because we had to attend workshops for it. Oh, and we teach throughout the year in order to make a meager sum of money! I had almost a hundred students last year, and since the course I was TAing was divided into halves, it meant TWICE the marking. (Don't ask me how this works, it hurts my head.) So yeah, things get slowed down. You can indeed finish in four years if you're a magical wizard (and as it turns out, such people exist), but most finish in seven or eight. I'm on track to finish in six, which is when my guaranteed funding runs dry.
Anyway, the more you know.