I would think there are many reasons for not accepting Bitcoin as payment. Volatility (how can you price anything when Bitcoin changes value so much?), long transaction times, and high transaction costs would be the main reasons. Personally, I would never accept Bitcoin because it's electricity usage is bad for the environment. It just seems unethical to use it.
Most store uses electricity every single day there's nothing wrong in accepting different kinds of payment. I respect their decision if they're not ready to accept bitcoin we can still sell our bitcoin for fiat to buy their products if we want to and it's cheaper than making a bitcoin transaction.
Well no shit imagine ordering a coffee and waiting like 6 hours for all the six confirmations. Alts for cryptocurrency will be faster than BITCOIN anyway
From my experience waiting for confirmations are much faster now and you could easily get 4 confirmations within an hour if you put enough fees.