A lot of people don't answer calls from unknown/blocked/private numbers. I know I don't answer them and I know most of the people I know don't answer them. If it's important then the caller will try again... from a proper number.
And most large businesses/organizations (along with many smaller ones) can subscribe to services which unblock and identify incoming callers. They pay good money (and the telecomms make good money) for technical/legal privileges which completely ignore user settings on consumer devices.
