Another thing is that if you have a render trudging along in your own place, you can check now and again how it goes, and if you suddenly see an overlooked mistake, stop and rework. It's also nice to see it come to life. And for render farms you need a card to pay. I don't have one, so it's out of the question anyway.
But surely for animations and really big renders it would be handy to have it done.
