Not only for illegal things, but in general. Monero protects the people who have nothing to hide.

Example

You want to sell your motorcycle to a stranger. Do you then prefer to accept Bitcoin, which may have last come from a drug deal? Probably not. If you accept Monero, you are protected because it is fungible like cash.

Anyway, we all have the same enemy: the fiat money system. But Monero is not here to replace the entire fiat money system. Monero is here to replace fiat cash and build a new economy based on digital cash.

If we want stocks, bonds, securities, tokens etc. we need something else. Maybe Ethereum is doing a thing here. Maybe Nym is coming. We will see.