well i think because bitcoin so far is just a prediction game
people buy bitcoins to invest by expecting rising bitcoin prices (speculation)
a good currency must have a stable price
That's why Bitcoin is not a legit currency
Yes Bitcoin has become an investing asset than a currency among many users in te world even it's build intention ws to become a global currency so how come bitcoin can become a legit currency when even its users are not accepting or using it as a currency for transactions