It only supports Bitcoin? Really absurd choice. The demographic of people using Proton services, using cryptocurrency, and only holding Bitcoin has to be pretty damn small...
If you're going to support one, support Monero, and allow paying for service with it. Then expand to Bitcoin, which is one of the easiest ways to buy Monero if your country is anti-Monero for some reason.
It makes more sense to not spread even thinner chasing AI grifting and cryptobro services when your existing services have been lacking basic functionality for years