hluch

No. Darknet markets also sell things that are unambiguously legal to buy everywhere, as well as products that are legal in some countries but not others. The products on sale are far from only the stereotypical drugs porn warez and fraud (and no you cannot buy assassination on darknet markets; any such offers are a mix of law enforcement stings and scams which take place without any marketplace providing escrow).

If nowhere but darknet markets let you buy a car with Bitcoin or Monero, then only darknet markets are what someone who has cryptocurrency and wants to buy a car with it will use. That being said, you can exchange cryptocurrency for a car safely and legally, without touching a DNM or doing anything shady.

There are several use cases.

1. Paying merchants who don't accept any other cryptocurrency (which is the majority of the available ones; typically they accept fiat in some form, plus Bitcoin since it's been around so long, but have barely heard of others).

2. Donations, same as above.

3. As an onramp from fiat to other cryptocurrencies, where those are accepted and Bitcoin BTC transaction fees for 1 confirmation in a reasonable time are an excessively high portion of the transaction amount.

4. For cryptocurrency payments which need the very highest possible level of security against double-spends, which is provided by Bitcoin's hashrate and decentralization, arising from there being a mature community around it. As far as I can tell, none of the other currencies have equally good metrics, though they do approach it.

Plus a few more.

And not forgetting that Bitcoin Core could in future raise the block size, making each unit increase sharply in utility and value, beyond its natural deflationary increase.

Less than 2% of "money laundering" is ever caught. That's despite the enormous time, money, and loss of dignity and privacy burdens, which are overwhelmingly borne by people with no connection to crime whatsoever. "Anti money laundering" is a parasite on humanity. They should let it drop to 0% and not bother with any of it: they doubtless keep lying to themselves that they are doing something worthwhile; they are not.