It seems to me Verizon doesn't care. I subscribe to WhitePages.com, which I did in order to check the identities of callers. It turns out that almost all are "unassigned".(technically a valid number but with no current owner) or "invalid" (there is no such combination of area code and prefix, or sometimes the area code itself doesn't exist).

My Android "Phone" app has an option under "Settings | Block numbers" to "Block unknown callers" which I thought would cause any caller not in my Contacts list to roll to voice mail. It doesn't do that. I'm not sure what it does, exactly, but it seems completely useless.

The fix for the problem would be trivial. Our phones already display the contact name for anyone on our Contacts list when they call, so obviously it is perfectly reasonable to provide an option to simply block any number without a matching entry in the Contacts list. Maybe they are getting a kickback from some of the scammers. I honestly can't think of any other reason not to fix it.