Well that's a great argument. How is a strong exclusive library not a selling point for a console? Plenty of people picked up PS3s for Uncharted and other exclusives (myself included), why shouldn't Microsoft be trying to create the same type of value with the Xbox One?
Sony spent tons of $ investing 1st party studio very early on last gen, and it took them 2-3 years to be fruitful. MS mainly focused on the 3rd party exclusivity since that was 360's edge over PS3 at the time, but now it bites them in the ass.
Buying great IP developed by 3rd party on a less popular console won't end well for MS either, just look at Demon Souls.