And when faced with competition from legitimized currencies, that somewhere is black market goods and services.
Eventually, someone asks the question, "Why can I buy weed with Bitcoin, but not pizza and chips?" And delivery of munchies is a legit business that can be advertised. Once recognized as a viable model, it can then be poached by major corporate players as part of a local pilot program, which can then be rolled out to larger jurisdictions.
The problem, as usual, isn't that you can't buy anything with it--it's that you can't buy everything with it. As long as you can't pay your electric bill with cryptocoins, the business that accepts one as payment can't also pay its employees with that same cryptocoin.
Honestly, would you even apply to a job posting if it said salary to be paid exclusively in Floopcoins?
Keep in mind that usage of "legitimized" currencies is being actively constrained, there are limits on cash transactions, they are/can be easily seized.. every time this happens crypto looks better in comaprison.
And in Europe one already can pay electric bill and pizza with crypto. While only few utilities already accept them directly, many more enterprises want to establish themselves on this emerging market by mediating these transactions.
Yet. Everything needs to start somewhere.