Are you a pilot or ATC? They’re different, but you build a visual representation of traffic in your brain in both arenas. As a pilot you cannot rely on ATC- you have to fly the plane first and keep yourself safe.

Not the GP but I've been a pilot for about 6 years and have friends who are controllers, and being a controller is entirely different, and pretty difficult.

You can fly VFR without services and you really only have to worry about yourself. There's no equivalent as an ATC. You're often working multiple frequencies on your own. Even if you don't typically do it on your own, if your coworkers gets sick now you are. I've had friends manage two tower frequencies as well as ground due to staffing issues.

Not to mention the fact that when you become a controller it's much like the military where you get assigned a place and you go there. You get preferences of course, but there's only so many suburban airport controllers needed - somebody needs to be in JFK tower and somebody needs to be in the middle of nowhere Montana and they're not flying in for their shift the way pilots can.

I'm inclined to trust the FAA's data that it's just not feasible to dump training resources into someone who statistically is either not going to make it or is going to quit if they don't get their preferred assignment and find out they need to move their family to Utah.

Pilot but trained for ATC in my 20s.

I assure you the mental picture you need to keep in your head as a controller is far more taxing than single pilot operation when you are primarily concerned with your own separation. A controller can be managing a 1 to 2 dozen aircraft, dealing with pop up IFR, flight following, traffic advisories, handoffs, etc. There's a reason you get a mandatory break after 2 hours.

It's not about the mental task. It's about selecting for a demgoraphic group that's more compliant and less likely to take risks. They want to lessen their chances of having egg on their face because they hired some young cowboy who, when faced with some impossible set of bureaucratic constraints decided he'd shirk whichever one of the conflicting restraints they didn't like rather than just take the KPI hit.

The under 30 crowd has a lot more of those types than the over 30 crowd.

This can't be the reasoning because the policy is to select /for/ under-30s, not over-30s.