Skeptics and Microsoft will point to ten year agreements to keep Call of Duty on as many platforms as possible. Ten years is really not that much time. Ten years ago the PS4 and Xbox One launched. Ten years from now the PS7 might be coming out. Imagine the news that Call of Duty will not be coming to the newest Playstation. That's one series. All other new and existing IP could be locked down.

Call of Duty is a huge franchise that makes bucket loads of money on yearly games, season passes, DLC, other monetization, merchandising, esports, and more. It's so much bigger than the ZeniMax catalog. Microsoft have no reason to gate 50% of the playerbase for "hardware exclusivity" given that lucrative revenue channel.

The reason is to get (eventually, almost) 100% of the player base.