Some history of the Haas Act here: https://www.politico.com/states/new-york/albany/story/2013/0.... One thing to note is that this didn't happen in a vacuum. This was happening at a time when the government regulated things in ways it wouldn't dream of doing today. If you wanted to build a new telephone line, operate a new freight trucking or airline route, or build a new railway, you'd have to ask a government agency for permission, and also get approval for the prices you wanted to charge. The agency would decide "oh, there is no need for a route from here to there" and could deny permission on that basis, or decide "oh, this price is too high, you can't charge that much."

The government back then generally viewed competition as a pernicious thing. So they imposed entry requirements to limit competition. That necessitated also bringing prices under government control, to curb monopoly abuses. The Haas Act followed the same basic logic. Limit pernicious competition by limiting licenses, but curb potential abuses by controlling rates.