i have a first.last@gmail address and my name is very common. So i bet others had to use less desirable gmail addresses.
Since google started to aggressively push for adding alternative email and/or phone number, dumb users that initially wanted my email address entered it as their "alternate email" not understanding it's for password recovery only.
I clicked the "not me" link in more than 20 confirmation emails, but google probably never used that to better inform the dumb users.
Now my gmail account is a cesspool of emails intended for other people, site registration confirmation for idiots with same first/last name but a different middle name... And there's no spam algorithm that can fight that!
Time to start looking for alternatives.