My experience as well. I can think of 2 reasons:
1. Phone number can be matched with off-market data sale of transactions
2. Emails have filters to auto-delete marketing emails, text messages still do not have a parallel.
I disagree. They can use a captcha at account creation to stop bots. They want to make money by tying together your activities with grey-market financial data and then show advertisers on how accurate their ad-targeting is.
