If I had a small business as a physical shop, I would simply go to bitadress.org, generate a new paper wallet, and print the public key in a paper, put it in the counter and that's about it. I wouldn't even bother dealing with 3rd party payment processors. The more you stay true to Bitcoin only the better unless you really need to.
That is what I would do also. However let me offer a defense of payment processors.
I have talked to a lot of businesses about BTC and they often have the same concerns. One realistic concern is price volitility. For a business the money never stops flowing in and out. They need most of each sale to cover fixed costs and new stock. It would be disastrous to get a lot of business in bitcoin then watch half of it go away in a crash. Many businesses can't weather that uncertainty.
There is also the problem of managing a wallet. This is all so new, and with money on the line it can be scary to amass bitcoin. Someone at the business would need to know how to safely collect, store, and cash out bitcoin. It may make more sense for a place to farm out the bitcoin processing for low fees. My guess is that the future will see a diversity of systems from "roll-your-own" to "never-touch-bitcoin" processing.