You claim that the only possible uses of cryptocurrency are to circumvent the law. If that were the case, governments would have simply made holding or trading it illegal -- but with few exceptions (bitcoin in China), they have not done so.
This is not your original question -- you have smuggled the word "impossible" in there, hoping I wouldn't notice.
Plainly a thing can have value even if what it can do can be done in other ways. It might be more convenient than those other ways, or cheaper, or be more reliable. It might involve having to trust fewer commercial third parties like banks -- which, you'll notice, has no implications for lawfulness.
As I already stated, crypto can be used as a store of value like gold, or for exchange like cash or barter. Neither of these uses are necessarily illegal.
I'm done here.