The use of Bitcoin

Bitcoin is a digital currency.
Bitcoin has a limited supply.
Bitcoin is volatile.
Bitcoin always needs internet.
If government legalized and use bitcoin like fiat currency,to what extent it can be used? I just thinking that it was very difficult if ever it will happen someday especially for the young children's. Unlike in fiat currency even a two years old kid can buy in a store using it but if bitcoin,i don't think so ,even those old people who do not know how to use a cellphone,computer and other gadgets. It will be difficult for them.I'm just curious guys and want to know your opinion.