The thing is, pushing the cart to take groceries to a car is a must for a person isn't it? The same can't be said for returning it, and while I respect a lot that you seem to have returned the cart every single time even if there is no nearby return spot, I don't see everyone being that way, especially when some stores barely have enough cart return spots on parking lots with PAID staff who are there to collect leftover carts.
If I am being honest, when I do physically grocery shop, in most cases since I mostly order online, when I really only have to, I do physical visit and I don't buy much, I just carry them with my hands to the car, I never had this issue lol.