Because the future will be very dystopian if we place two tech companies as gatekeepers of everything in life. If Google locks your account and won't help you (which happens!), you don't want that to also take away your ability to bank, go to baseball games, etc.
If that is your threat model (it isn't for 99.999% of people), you can set up your own email domain for few bucks a year and it takes 20 minutes. Now no one can debank you and take away your ability to go to baseball games simply by killing your email.
But that's not the reason the guy in the video isn't using a smartphone. It's because he literally never bothered to learn or keep up.