It's very possible that our coins are already mixed with illegal coins those were marked on the addresses. You never know.
When we deal with cash, we do not know the source of that cash whether it came from an illegal or legal source one hand before me.
Exactly as you said, in real and physical market, peolle exchanges both stolen and salary paid money together, who cares? So far as it provides liquidity and fast execution, who cares? There's is an African proverb saying, " even if money comes in dirty bags, you must welcome it". This had never been a bother in me, and never mind OP.