Bitcoin is not suitable for small businesses and small transactions due to fees. You might end up paying more fees than the actual amount you're supposed to pay for a particular transaction. And by the way, adoption is quite different from being used as a legal tender. One can exist without the other.
There is Bitcoin Lightning Network and there are layer 2 projects too.
Sidechain Observer - Bitcoin L2 Projects & current state of development.There are times when altcoin blockchains have more expensive transaction fees than Bitcoin blockchain. You can see the average transaction fees in last three years of Bitcoin and Ethereum blockchains.
https://bitinfocharts.com/comparison/transactionfees-btc-eth.html#3ySmall business have to use and rotate their money faster than big business and they have less capability of dealing against price volatility and effects on their business treasury. Their customers can be considered pros and cons of using bitcoin as a payment method at small business.