Console exclusivity of games is a way to provide an incentive for purchasing your console.

Imagine you’re a business and you spent millions on the R&D, manufacturing pipelines, shipping logistics, marketing, etc for this cool new console but you’ve got nothing on it by default that people can’t get elsewhere. In this situation, the first console to launch in a given generation would win. If you profit off of the console (you should), any exclusive that converts a user is price of console + price of game gross revenue.

This helps explain why we’ve had exclusives, but the winds are changing. These game companies which make both games and consoles see the short-term profits from your aforementioned wasted opportunity as more valuable nowadays while largely ignoring the fact that a lack of exclusives will make their consoles less desirable.

IMO the PC is going to basically cannibalize the console market (everything goes there and goes on sale, emulation included) and PC hardware can be made to last for a very long time despite a higher initial investment. If Valve can get a Console-like experience that’s plug-and-play with a TV, then Sony and Microsoft are in a bit of a bind.