No, security is pretty easy and has been for decades. PGP has been a thing since 1991, and other encryption schemes were a thing long before. ProtonMail uses PGP and SMTP, the latter of which predates PGP by about a decade (though modern SMPT with extensions wasn't a thing until 1995).

So at least for email, there's little technical reason why we couldn't all use top of the line security. It's slightly more annoying because you need to trade keys, but email services could totally make it pretty easy (e.g. send the PGP key with the first email, and the email service sends it with an encrypted reply and stores them for later use).

The reason we don't is because servers wouldn't be able to read our email. The legitimate use case here is searching (Tuta solves this by searching on the client, ProtonMail stores unencrypted subject lines), and 20 years ago, that would've been a hardship with people moving to web services. Today, phones can store emails, so it's not an issue anymore, so it probably comes down to being able to sell your data.

Many to many encryption is more complicated (e.g. Lemmy or Discord), so I understand why chat took a while to be end to end encrypted (Matrix can do this, for example), but there are plenty of FOSS examples today, and pretty much every device has encryption acceleration in the CPU, so there's no technical reason why it's impractical today.

The reason it's not uniquitous today is because data is really valuable, both to police and advertisers.