I remember when curiosity got me way back in the very beginning of Twitter when the church I was going to at the time was trying to be all trendy and innovative with social media, and I remember trying to sign up and it needed your mobile phone #. I said F-that and never looked back.
They ask me to provide it every now and then. I never have. I say no. You have the option.
But if you think all these places can’t get that info you’re nuts. ;)