I don't carry quarters on me - I'm not going to change that just to use a shopping cart
I usually bring my kids with me when I go grocery shopping. I can barely keep them together and focused as is. I'm not going to bag my own groceries in a different location from where I pay and I'm not going to leave my kids in the car while I walk my cart back to the store to get my quarter back.
And yes, I'm doing grocery pick up as much as I can - usually at my neighborhood's HEB.
Saving a few bucks in exchange for far less choice and an added layer of hassle is not worth it to me.