It doesn't appear to be regional in my area though that's my personal opinion.
Somehow people can manage to never leave a cart in the parking lot at Aldi. And yet they leave their carts from time to time at other places. More often than not I see people putting the cart in the designated area. It's less common to find random carts from what I see though it does happen. I guess I could say the people who do that are from a different region originally than right here in our area lol.
I don't like finding the convenience of finding a deserted one in the parking lot because it's never in a more advantageous spot than just getting a cart from the designatated spot if I'm getting the cart from the parking lot as opposed to inside the store. When not put back in the designated spots they are often in parking spots themselves, half up on an island though still blocking parking, all the way up the island blocking the walking path put in place, put next to handicap spots in the stripped lines so now someone has that obstacle to contend with, or for whatever reason just outside the designated spot (can't seem to figure that one out lol).
Then again I'm not sure if that's worse than the people who walk out the exit of the store while grabbing their bags and then just leave the cart there rather than putting it in the cart area several feet away lol. You can't use the excuse of "there's no place to put my cart" for that one.
Perhaps people are just more careful where they put their carts in your area though in comparison to mine.