Too many people. Example apply for job. Even in Europe, so many employers ask for PDF of all your certificates by email.
BTW, not everyone works in SV or FAANG that uses top encrypted databases from some top recruitment agency. Sure there are 10 jobs in government sector that will ask you to print 100 page of application - hand fill and send it. Everyone else not.
BTW, at my local copier place in Berlin, people come with file in cellphone. They just email or WhatsApp the PDF - can be CV, passport or anything - to the common copier fellow's email/WhatsApp - then print.
Even at most covid testing centres at airports - you need to give your passport number + address etc. You think they use encrypted laptops or GPG emails. The test result is returned by PDF email.
Sadly, proton mail is like iPhone. Sure it is secure, but once you install facebook or tiktok - nothing can be done.
While some whistle blower can use protonmail to send email to some journalist - for the normal citizen it is just useless.