It could be because they are gutless unimaginative trend-following sheeps.
It could also be because they just try to sell whatever it is they think most of their customers believe they want / need (wether or not said customers are right is a whole other matter)
Even if you do, they're still not necessarily exclusive: ifixit tore down a bunch of HP devices, and even the "Elite X2 G4" two-in-one — not exactly a beastly looking device https://www.notebookcheck.net/HP-Elite-x2-G4-detachable-will... — got 9/10 on repairability: https://www.ifixit.com/News/hp-makes-the-modern-repairable-d...