I think everyone who answers this question will have one answer because nobody is interested to invest in fiat currency because it is not value but bitcoin is store of value. And people invest in bitcoin to make profit and that is the ultimate goal for all investors because nobody would like to invest in a business and lose from the business.
Though some people use it to hide their stealing funds and launder money. And some people because of the high cost of bitcoin to invest, choose altcoins to invest while some invest in altcoins to make quick money. And those who hide their money there probably politicians because of the decentralized nature of bitcoin.
Actually, there are many people who has no ideal about cryptocurrency, how it works, where to start, who to teach them about cryptocurrency etc, these set of people are still saving their earnings on Fiats
Also there are still places in world today where there are limited internet access, I mean in the rural areas like in Africa, some part of Asia; the people on this areas still save on Fiats
Now, concerning money laundering, it is not that there were no money laundering activities before Bitcoin was invented, but I think many haters of Bitcoin, especially the Fiat wealth men/women had wanted to discourage crypto adoptions, there by tagging Bitcoin as a means of laundering money, and sponsoring terrorists groups but unfortunately, crypto was able to absorb those negative informations.
In a nutshell, before Bitcoin was invented, there were much terrorist activities, plus money laundering and stealing. These criminal activities has always been there, and various means has been used to hid money, Bitcoin was added because adoption is increasing globally.