Combating bots by banning anyone without an email is understandable and seems doable for the near future, but like it would mostly be a hiccup for the people churning them out.
Google ignores any periods in an email address, so if you want to sign up with the same email all you have to do is fill it with differently-placed periods. What are they gonna do? Ban everyone who shares your name from having a reddit? Ban Gmail? If they did, there's still the plus trick that isn't specific to gmail