Are they not blocked for being VoIP?

I've only run into one instance where they wanted a real number. (Coinbase) I think sites only block those when there's a reason to.

If my banks are all willing to use my Google voice number, then any other site should be willing to as well. And yet, most websites that want a phone number won't take it. My GV account is in use for WF, Discover, PayPal, Steam, and it was previously in use at BofA when I had an account with them.