It's not everyone that will adopt bitcoin which will make it impossible for everyone to use bitcoin to pay for goods and service online. Bitcoin blockchain is not designed to carry to big load of transactions and that will become a problem if everyone start paying with bitcoin.
High transaction fee have discouraged a lot of people who planned to add bitcoin as payment method to their businesses because if the blockchain is congested, payment with bitcoin becomes fucking expensive. Lastly, if businesses start accepting bitcoin as payment option, many bitcoin hodlers wouldn't want to spend their bitcoin, because they want profits from it.
If we want to adopt Bitcoin as payment option then issues like transaction speed and fee can be fixed with Layer 2 solutions like Lightning network. As long as government regulations are not in favour of bitcoin, it's difficult to use Bitcoin as payment option. The countries which have legalised the use of Bitcoin have done that after introducing pro-government regulations which make Bitcoin or other crypto very much same like fiat. This is main reason why people are mostly using bitcoin as an asset of investment.
Setting up a LN is not free, you have to pay for it which makes me feel that cash is the best to use when paying for little amount of stuffs. Government does not need to legalize bitcoin as a legal tender first before you can use it for payment, as long as crypto is not illegal in your country, anyone can accept bitcoin as a payment option.
Currently, my country hasn't been too supportive in cryptocurrency adoption in the country, but it's not illegal and one can use bitcoin for payment here but you will hardly see someone who will accept it, because they prefer fiat to bitcoin since they don't trust you.