Not just because it can buy water means it is mainstream because it is a need to be adopted by worldwide and not just in specific place , remember that there are countries now that already having this existing like in El Salvador yet is this already mainstream? maybe in their country but worldwide is something we still waiting.
People aren't buying water bottles with Bitcoin in El Salvador or anyplace else. You don't need a government to buy up a bunch of it like they did in order to make Bitcoin mainstream, you need to make it perform comparable to credit card transactions at a comparable price, which Bitcoin is at least 1000x from being.
Everybody knows the name "Bitcoin" and it's a meme worth over one half trillion dollars. What more do you want?