Don't be mistaken, actually using this for public images is falling for another "data gravity" marketing gimmick. So they attract enough public images that some folk find one or more of their services absolutely must pull from AWS, pushing their corporate NAT address over the 41GB/day limit. Now your "free" hosting has become a reason for that company to start paying ~$45/month to AWS in egress fees just to use your images, and perhaps with a new ticket in the backlog to consider simply moving the cluster to AWS.
"But it'll always be like that regardless of provider", not necessarily. The reason that Docker registry consumes a ridiculous amount of bandwidth is largely an architectural issue, both in the software and the design of the client's network. Perhaps a better direction is addressing this immense waste of networking rather than turning it into another free marketing opportunity for a near-monopolistic cloud