An improvised model for explaining the seemingly exponential growth is the belief that there is inherent risk of being forgotten as a currency but that this risk falls exponentially with time or price itself.

There no reason why that risk should fall.

Bitcoins has such risks as a mathematician inventing a way to break public key crypto that would completely destroy it. Again if people build useable quantum computers, bitcoin is gone.

For being an digital currency bitcoin has massive amounts of transfer costs. It's possible that someone creates a better online currency.