They do make their own donations, separately, often. Customers’ donations are just another way.

I guess think of it from the charity’s perspective. Checkout donations are steady fundraising for them that supplements their other more sporadic and difficult fundraising attempts. I imagine they solicit the stores to do this for them when they’re not organizing 5Ks and hosting dinners for rich people.

If it’s upsetting that stores get to promote themselves for doing it, then just donate directly. Same difference.