Probably because we haven't been using the terms long, and/or because there's a lot of misuse of the terms out there.
Not all digital currencies are cryptos but all cryptos are digital. Libra is "just" a digital currency, in that it doesn't have what it takes (like decentralization or privacy) to make a currency a crypto.
While no crypto has yet been created to be perfect, Libra is just complete garbage compared to what's out there on the free market already. The only reason it's going to succeed is because of their captive audience (2+ billion FaceBook drones who have been abused, censored, and lied to for years but remain loyal).