If you are not a criminal, it's not called money laundering. If all your money sources are legit and taxed, you can't or will want to launder the money, you will just use it and nobody will have any problems with it. Earning money and not paying tax on it, while still living in the country that needs those taxes and using the services it provides for those taxes is a crime though.
Anonymizing the coin is to bring back fungibility which is lost in cases like high profile users (Satoshi and his $100.000.000 in bitcoins) and stolen money. I don't want my money be confiscated just because I sold my music anonymously to pirate@40. If I were Satoshi even after paying taxes on my fortune I might not want to reveal who I am. Very unlikely this info wouldn't leak even if he made efforts to secretly pay taxes.