Just to make sure of a couple of things

-that 40% on income is after you remove the price of hardware and electricity right?
-when you pay your tax you also contribute to your social security and retirement plan right? I'm not to familiar with the american system, but here in europe when you work and you have your gross salary and net salary, and the different is to pay off for all those + tax (well at least in some countries)?
-I'm not promoting tax evasion here, but how can IRS know how much you bitcoin you've mined 

Privacy is critical for the proper operation of the Bitcoin system because all account balances are public.  If we cannot maintain privacy then Bitcoin will fail.  Would you keep your money in a bank where anyone in the world can simply look up your balance online?  Would anyone run a business using a bank where anyone, even competitors, can look up their current balance and see all of their income and expenses anytime they want to?

Nobody will use Bitcoin without privacy protections.

Anonymity is a different but related concept.