Why is anyone using encrypted e-mail anymore, anyway? Reliably and easily encrypting e-mail is an insurmountably hard problem for reasons having nothing to do with today’s announcement. If you need to communicate securely, use Signal. If having Signal on your phone will arouse suspicion, use WhatsApp.
I wondered the same thing, though I do use ProtonMail. Signal is great, I question WhatsApp’s long term changes which might cause encryption woes later on. But I can answer why use encrypted email: for many people it’s easier to type out emails on a laptop than tap them out on a phone. Signal is trying to overcome this, but I think it is an uphill battle. Still, way better than encrypted email.