That's true, but imagine how that would work out. For months you pretend you don't make any money and all of a sudden you buy a house worth half a million euros. Do you think nobody is going to notice at the government?
Do you know about the Toine Manders case? They don't have evidence of any crimes, but they basically ruined his career because they suspect him of tax evasion.

Blockpay sounds really cool! I'll check it out.