A big problem in making crypto's 'exchange currencies' is the big ups and downs. Fiat money is still the standard and there will be a transition period for a while. Many platforms don't start with crypto support as a means of payment until the crypto/fiat exchange course isn't more stable.
And the HODL mentality is also a result of the extreme ups and downs. If you expect that US Dollar will have 10x the value they have now by the end of the year, you will HODL them.