There are certain things that are known facts, there is no need to prove them every time.

The simple fact that:

• There is not a standard tool that is common
• The amount of people who use PGP is ridiculously low, including within tech circles. Just to make one example, even a famous cryptographer such as Filippo Sottile mentions to receive maybe a couple of PGP encrypted emails a year. I work in security and I have never received one, nobody among my colleagues has a public key to use, and I have never seen anybody who was not a tech professional use PGP.

You can also see:

• https://www.latacora.com/blog/2019/07/16/the-pgp-problem/:

We can’t say this any better than Ted Unangst: "There was a PGP usability study conducted a few years ago where a group of technical people were placed in a room with a computer and asked to set up PGP. Two hours later, they were never seen or heard from again." If you’d like empirical data of your own to back this up, here’s an experiment you can run: find an immigration lawyer and talk them through the process of getting Signal working on their phone. You probably don’t suddenly smell burning toast. Now try doing that with PGP.

• https://fosdem.org/2024/schedule/event/fosdem-2024-3297-sequoia-pgp-rethinking-openpgp-tooling/

A recent talk, I will quote the preamble:

Although OpenPGP is widely considered hard to use, overcomplicated, and the stuff of nerds, our prior experience working on another OpenPGP implementation suggested that the OpenPGP standard is actually pretty good, but the tooling needs improvement.

And you can find as many opinion pieces as you want, by just searching (for example: https://nullprogram.com/blog/2017/03/12/).

However, if you really believe I am wrong, and you disagree that PGP tooling is widely considered bad, complex and almost a meme in the security community, you are welcome to show where I am wrong. Show me a simple PGP setup that non-technical people use.

P.s.

I also found https://arxiv.org/pdf/1510.08555.pdf, an interesting paper which is a followup of another paper 10 years older about usability of PGP tools.