Those guys would still only play a couple of matches per year. And the money that T20 brings in means that he'd probably have to go to work a few days a week.If T20 didn't exist he'd likely be playing Shield against the likes of Steve Smith and Pat Cummins on a regular basis. I'd consider that more valuable then rubbing shoulders with some Afghan Players and James Vince, no disrespect to them.
You can mock those guys all you like but they are experienced professionals who play all around the world, playing with and against the absolute best in the world. Living in their pockets and training with them every day for a couple of months would be invaluable to a teenager, much better than trying to grab some quick conversation after a day's play.