The entire idea behind credit cards is to force processing fees upon store owners. As a store owner you are required to pay up to 3.5% of your revenue to the processing company (the percentage can be even higher than that if you sell stuff for small amounts, like just a dollar). With cash you can choose your bank and there is more of a free market, while with credit cards you can't get around not accepting certain br…
The entire idea behind credit cards is to reduce friction in commerce resulting from handling cash. This attracts more customers to businesses through increased convenience.
Taking cards is voluntary, there's no "forcing processing fees" involved. Plenty of businesses opt not to take credit cards.
In fact, interchange fees (which in the US now top out around 2.7%, not 3.5%) are at an all-time low because of technology improvements. The first credit cards had a processing fee of 7% (https://www.businessinsider.com.au/history-of-credit-cards-2...).