That's like asking why would you accept credit cards, paypal, mastercards etc.... WHY NOT?
Well, credit cards and paypal are just a form of payment platforms for cashless transaction. They all still deal with fiat in local currency. However bitcoin is a totally different story, it's another currency much like you paying with euros for a beer in a bar in LA isn't it?
You could kind of put it that way but you'd also have to consider that accepting that Euro would give every European access to your business.. Which mean more customers equals more profit, which means your a successful entrepreneur with a growing business that is ahead of the pack of failing small business..
