I could be mistaken, but didn't the GC version also have cliffs? I don't just mean cliffs overlooking the beach either.
Yes, it had some cliffs within your town. I played it for a bit and really hated that, it made it more annoying to move around when you had to search for a way down to the next cliff all the time.
Why did they got rid of that?
Maybe because villagers tend to give you a chance to ask them to stay, though it's before they packed up. If you talk to a villager who is moving, they'll usually ask if they should stay after all.