There isn't any con of holding crypto that isn't already a problem if you decide to hold fiats. You're going to lose the value of the money you hold over time just as you can lose money if you hold crypto that isn't Bitcoin over a long period of time. Of course there are few other crypto that have done massively well because if you had bought them from their early introduction to the market, you'll still be on profits but they aren't many in the market. Crypto is bringing the whole together through borderless transaction that's instant without much fees being attached. What I believe crypto is doing is eliminating the need of middle man and that's what is making the transaction more decentralized.