> Gmail is one of the main reasons why email is used by almost everyone.
Are you sure? When do you receive e-mail from live person, not robot (yes, each online shop will spam your forever after one buy), neither notification from automated system neither forum and not related to you job?
I'm 45, and I'm using email from 1997, but I can not remember when I receive or send "personal letter" by e-mail for last, hmmm, five years? Yes, of course, there are tons of e-mails at my $job (but, again, mostly from automated systems, persons prefer Slack now!), there are ton of notifications, promotions, etc. Also, yes, I'm dinosaur and I'm using mailing lists for some "nerdy" and very old-skool projects, which is nearest thing to person-to-person communication in my inbox.
All real person-to-person communication with my (extended) family, friends, many groups of interest (not connected to IT, like hiking or off-road motorcycling) are in other media now - mostly Telegram groups. Not e-mail.
And before gmail (2004) I can not remember any person I want to communicate who was equipped with PC and didn't have e-mail. And ICQ. Which required e-mail to register, not phone number. Of course, my grandma didn't have e-mail in 2004, but she didn't have any device for it in 2004, either.