If it can't be used in the ecosystem, it still can be used outside of it by exchanging it for any other crypto that can be used as a currency most places.
But it was never intended to be used solely as a currency, but more as an asset. A lot of investors don't expect to sell the coins because of the incentives we get from holding them, like airdrops and dividends from staking coins.
So even if EOS doesn't behave like real cash on the ecosystem, it still holds its value.