Lots of hacks, lots of phishing, lots of people who don't know how to use crypto, which is one factor if crypto will never replace fiat. And as you said, crypto is only liked by everyone for investment
I agree with what you say, but hacking, phishing, and ignorance using crypto are not the right reasons. In fact, many people do that to take fiat from the bank. however, this technology is unstable, which is what makes many official companies reject it, such as steam when they accept bitcoin, and then put it out because of very volatile prices. just like you buy a bicycle, if today you buy it at a price of 0.05 btc, it could be in a few days the price becomes 0.02 or even higher than 0.05 btc.
The main issue is still its high volatility. It causes more fear and gives a drawback. Not everyone is bullish about cryptocurrency, most especially bitcoin. For the fact that we still have people who panic sell or buy too hastily, there will still be difficulty in adopting it as a replacement for fiat.
Fiat is more stable, which is why it is used to back up some stablecoins . We still need fiat irrespective of how useful crypto might be tomorrow. It will only be used as an alternative, perhaps where it is accepted.