While valid and interesting (good to know, and to share) for most people GNUPG-signed+encrypted emails are nice as a privacy protection tools against mass data mining. Even in today's society I't a bit hard to imaging Alphabet, Yandex, Microsoft etc do such kind of attacks...

Yes, but i believe tools/features like these advertise a sense of a level of security to the user which is, evidently and also to the protocols involved inherently, not what they might be led to believe. Given it's usually sensitive context, this can be quite dangerous.