Who exactly wants Libra?

Crypto enthusiasts know better than to trust a centralized coin coming from a company with very questionable privacy practices.

The mainstream could continue paying with Paypal and credit cards since it's all the same anyway. This way, they won't even need to pre-convert any money to Libra.

Lastly, since it's a stablecoin, it's closed off to speculators. You could argue that it might be able to replace Tether or some other stablecoins, but a lot of people use those to dodge regulatory mess that comes with trading fiat, which also comes with trading Libra.

Just because Facebook is used by billions of people doesn't mean they'll use whatever product Facebook comes up with, and the same is true with Libra.