I'm going to be rude but IMO it's mainly because of "stupid investors" putting their money in doubtful ICO's which "suprisingly" collapses.
Then they go and inform authorities demanding to help with getting their money back. (instead of accepting they made a bad decision and silently move forward).
Great paradox is when the ICO is actually successful, a lot of people would try to hide the profit from gov. (to avoid taxes) ... but when something goes wrong (please gov. help me
... it's you job to protect me ).
What else can governments do when courts are flooded with such complains? They have to react somehow and this is the only option (alternative would be BAN "stupid investors" from holding significant amount of money
... but that's impossible/unacceptable ).
I'm a great example. Invested in Mycelium crowdsale ... bad move.
But am I complaining? NO (at least not to authorities). It was MY OWN MISTAKE and nobody forced me to. So I can (have to) live with that.