It's definitely worthwhile to understand why a site is asking for your phone number. At the company I work at, we require a phone number because a lot of our cu

It's definitely worthwhile to understand why a site is asking for your phone number. At the company I work at, we require a phone number because a lot of our customer's don't have email addresses and/or have given us a bad email such as no@email.com. We use it to contact customers in collections BEFORE the bad things happen like shutting off your power. Some sites will use your phone for two-factor auth although I doubt you're complaining about those sites. Many SAAS companies will ask for your phone number so they can upsell you. The good news is that there are some options if you don't want to give out your phone number. 1) Give out a fake phone number such as 555-555-5555. This works assuming you don't need to verify the phone number. 2) Sign up for a google voice account and pick a phone number. You can get texts and receive voice mail and read them through email or by going to google.com/voice