Of course if your money starts in your "books" before being converted into cryptocurrency then yeah, it's useless. But that's not the use case, it's more about laundering money that's not in the books to begin with (corruption, black market, undeclared sales etc...).
I believe that right now the main deterrent to this scenario is the same reason people don't use cryptocurrencies for legit use cases: it's wildly unstable and you have to convert it to dollars or some other "fiat" to do anything with it.
However, if you want to receive bribes, you just create a new wallet, you receive the bribes in BTC and either change them somehow in dollars or pay a premium to receive some services directly paid in btc (I am sure many people would be happy to receive BTC payment at a 30% discount).
Tax evasion works the same: you receive some payments that you do not declare in BTC. It works exactly the same way people use cash to evade taxes, except that here you don't have to transport luggages full of banknotes.
Another feature of BTC is that it can't be seized. Cash, gold, paintings, they all can be. BTCs are much easier to protect.
You would have to be a total moron to go through all the hoops to use it otherwise. Its kinda like running desktop linux in that way.
For the same reasons it sucks for individuals (volatile, slow, expensive, publicly recorded, difficult to spend and difficult to convert), it sucks for criminals.
So, what, you'd have to be a total moron to go through the hoops of installing Linux as well? Do you think before you comment?
Your 100% figure is wrong given that I, at least, don't match any of your description. You can't go around claiming this kind of nonsense.