Whats the chances of shops trying out bitcoin if they have to run around putting new prices on everything hourly? "They can just display the exchange rate" doesn't cut it, if vendors can't display the prices in BTC then it will be a second class currency. For now the fluctuations are great to get interest and investment but crap as an exchange of value.
The higher the value of Bitcoin rises, the smaller relative changes in value are. At $10 000 per bitcoin a change of $10 in BTC price is 0.1% in total value. Any shop understanding this will understand that they have minimal risk in accepting bitcoin, as it is likely to go up in value, not down. So if they don't update their prices that often, they usually get extra money.
This is one of the reasons why buying BTC now is such a good thing. There's only two possible outcomes: $0 or A LOT.