Comment by AnthonyMouse

> I'm sure this comment will get downvoted in favor of some other conspiratorial "because they're going to secretly sell my data!" tinfoil post (this is HN of course). But my explanation is the actual reason.

Your explanation is inconsistent with the link in these comments showing Twitter getting fined for doing the opposite.

> Hence why even Facebook requires a unique, non-VOIP phone number to create an account these days.

Facebook is the company most known for disingenuous tracking schemes. They just got caught with their app running a service on localhost to provide tracking IDs to random shady third party websites.

> You can easily block VOIP numbers and ensure the person connected to this number is paying for an actual phone plan, which cuts down dramatically on bogus accounts.

There isn't any such thing as a "VOIP number", all phone numbers are phone numbers. There are only some profiteers claiming they can tell you that in exchange for money. Between MVNOs, small carriers, forwarding services, number portability, data inaccuracy and foreign users, those databases are practically random number generators with massive false positive rates.

Meanwhile major carriers are more than happy to give phone numbers in their ranges to spammers in bulk, to the point that this is now acting as a profit center for the spammers and allowing them to expand their spamming operations because they can get a large number of phone numbers those services claim aren't "VOIP numbers", use them for spamming the services they want to spam, and then sell cheap or ad-supported SMS service at a profit to other spammers or privacy-conscious people who want to sign up for a service they haven't used that number at yet.