Before purchasing my most recent laptop I tried going "without" for a bit and found that an iPad just didn't feel as smooth for video editing and some other work that I was doing at the time.
The closest analogy that I can think of is trying to go on a long-distance road trip on a motorcycle, when you're used to a luxury sedan. Could you do it? Sure. But it's just not the same ride.
RE: Do we still need computers?