The number one reason not to invest in crypto is the risk that every crypto have, investors always fight and accept every consequences once they invest in an altcoin, two possible things will only happen, success and lost.
Actually, it is not only in cryptoinvestment whereas risk is present but to any kind of investment. Risk is due to the sudden changes on the market value of every crypto which is a bit of a downside for an investment. Unlike in real estate or stocks that most of their price is stable, cryptos' market value are not. But if only investors wouls be commited and patoent, there's nothing to be worried of because dumps are not permanent.