I've never really been a fan of the way that platforms really push for collecting phone numbers.
https://lifehacker.com/twitter-used-your-phone-number-to-send-you-ads-now-wha-1838906777 A possible reason why they do so is for marketing, of course (also, security is not the only reason they might use to push someone to give them their phone number...).
I don't think Twitter in particular was even that aggressive about it prior to 2018. #privacy