I think, it's because of lack of trust to young players. What I have seen in last few years, above anything PAK think tank values experience more. Obviously someone starting career 10 years earlier is more experienced than a young player. In recent times, I have heard several times from reputed PAK former players like this -
Saqline : Younis should be there (in WC), because of his experience, because when a senior experienced player stands, he wins it (uo chaa jatey hai)
Shoaib : Hafeez is out of form with bat, but he has lots of experience to serve as a bowler - should be there (that's after this PSL).
X (forgot name) (May be Basit or Latif): Ajmal should be taken to WC. He has enough experience - it was just about passing his bowling action, which he had done - don't think he needs to prove it in domestics
X : Babar ko Lena chahiye (in UK tour); he is sr. pro with lots of experience. In England, experience comes handy ...
... I can go on, but don't want to mis quote anyone.
This is actually across all ranks (shouldn't blame Misbah only). Shahriar wants to keep Misbah as captain because he doesn't have enough experience to replace Misbah the Captain, for a side whose average age is well above 30.
Inzi thinks of calling back few experienced players for CT.
PSL teams' average age was close to 30 (despite couple of forced U19 players), for a youngman's game.
I am certain Babar won't have batted at 3 if Arthur wasn't there. And, Shadab can be as good as anyone with bat, still the first thought is - this kid will shake in fear without experience.