I use my gmail address to log into many apps, so they know my phone number. The problem is that some stranger with a similar name keeps using my gmail address to create accounts. So when I creating an account for a DoorDash pickup today, the app decided I was Elizabeth H, and my food was labeled Elizabeth H, and the guy at the counter argued that the old cis male in front of him didn't really look like an Elizabeth... I had the same problem with my Best Buy account, I can't use my gmail address to login to that because Elizabeth already has her account linked to my email address. Unfortunately, she hasn't left a credit card active for that account. One time someone no Etsy used my email address and was foolish enough to leave her credit card attached. So she received a surprise: poop soap delivered to her door! The data collectors can figure out a lot about you by aggregating data from multiple sources, so they do know your phone number, and can link it indirectly to you email.