And the really nice thing about this is that there are no fees.

If I just need $80 or so (I think the limit is $100), it's faster to go to the local Walmart and buy a candy bar or something and get back $80 cash than to go the closest ATM owned by my bank to avoid the double dipping fees.

Our local grocery store (Fred Meyer, aka Kroger) has started charging a fee to take out extra and get cash back. Not a lot, but a bit annoying. I used to get cash that way all the time, but even for a nominal fee I just avoid that store now. I am weird, yes.

Yeah it makes sense there are no fees for cash back. Walmart doesn't want cash, they want to get rid of it as soon as possible.

The ATM has to be actually refilled with cash, so they charge you for it.

That doesn't really make sense. My bank's ATM has to be refilled with cash and they don't charge me. Likewise, I doubt the Walmart self-checkout is sorting bills and only dispensing $20's: they also have to be loaded with cash separately.

The only charges I encounter are from using my bank's card at another bank's ATM.

It probably depends on the type of account you have with the bank. I certainly don't pay ATM fees so long as I use my bank's own ATM but perhaps there are more bare-bones account types that do.