The point here is not what the advantage of phone support is but to provide the service personally. You can outsource anything, but if you read the article, the learnings you get from doing it yourself are invaluably useful.
I (mis?)interpreted the GP comment to mean a service that makes it easy to charge for the phone support they provide.
Premium phone numbers are a lot of work to get setup, and payout rates are often no more than 1/3 of the call cost.