Living in New York City, I've noticed that there are a whole lot of businesses that are either cash-only or card-only.
I always understood the cash-only ones. If you can get plenty of customers who are willing to pay in cash, why would you want to pay credit card fees?
The card-only ones were harder for me to understand, until I realized that handling cash costs money, too. Somebody needs to count it all at least once a day, if not more. Employees can steal it. Robbers can steal it. You need a safe. You need cash registers. You need to get the cash deposited in the bank, by paying someone to go do that. You need to maintain an inventory of smaller bills and coins to make change. You need to train people on all of this.
Even just the accounting costs might make up the 2-3 percent in fees. "Your register said you made $150 in cash that day, but the deposit that night was only $135." That's what you pay accountants to deal with, rather than just exporting from your Square account to Quickbooks or whatever.
I had this realization because I went to a new coffee shop that had opened up. It appeared to be owned and operated by just one lady, and she was really nice. So, as I normally do for the nice local business owners in my neighborhood, I got out some cash instead of a card, thinking it would benefit her business. But then she told me they were card-only and it dawned on me: she's just one lady running a store by herself, _of course_ she doesn't want to deal with cash.
So, I'm not sure the 2-3 percent fees are all that bad, though I could be convinced otherwise. Plenty of small business owners seem pretty happy just setting up a Square reader and not dealing with the headache of cash. I think there's a lot of value in that for them.