In a perfect world, that would be awesome. Because PIs all work well together and all pull for the common benefit of the industry.
In reality, what we have is people that should never be PIs moving from states that require licensing, to states that don't. That means they can prey on people, move to a different city, print up business cards with a different phone number and seek more people to exploit. After all, associations have no power over members save for administrative methods. And frankly, speaking as a board member for 13 years, it's like herding cats to get everyone on the same page.
Looking at it from an advantage for PIs themselves to be licensed: I've had people that would not settle for an interview until they saw my license. I have to show it to clerks to get records. Sure, the THEORY of Open Records is alive and well, but we all know how theory rarely pans out into reality.