In previous eras (1980s, 1990s, early 2000s), hardware differentiation and game exclusivity were part of the same equation. Why? While costs today have risen due to inflated content expectations and modern salary requirements, previous eras saw much of their cost driven by the need to develop for different hardware scenarios. If a studio wanted to develop a game for Xbox 360 (for example), it was often very difficult (if not impossible in some scenarios) to run that same game on a Nintendo product, or even the PS3 (thanks Cell).
The further back in time you go, the more exclusivity made sense to the development team. They could focus on one build and a collective audience, while taking a payment from the console manufacturer for partnering with them (if they weren’t already owned by the console manufacturer). Keep in mind that it was often difficult to even get a version running on another console, or even PC, thus the focus on one build. If the money worked out, the development team could always try a “port” later (rebuild the game for another platform). Regardless, exclusivity was often a competitive deal for many developers. Hardware, for the most part, drove the underlying structure of how the industry operated.
Today, hardware is vastly more standardized and most of of the technology has coalesced around a handful of APIs. In fact, most modern engines already cross-develop across Nintendo products, Xbox / Windows DX12, and PlayStation. Building cross-platform isn’t like it was in the 2000s. Cost, primarily, is driven by large development teams (at least for AA and AAA products), not technology restrictions. A game team can cross develop a game from the inception of the concept, but they often have to pay 100-500 people to do it. Hardware isn’t driving exclusivity, unless it’s Nintendo. (Nintendo can do so because of their history, catalog, and hyper focus on hardware as a core product. That’s an article for a different time.)
Exclusivity today, for Xbox and Sony at least, is almost entirely due to back room business dealings, purposeful “walled gardening” or first party restrictions (all business focused purposes). The restriction of potential buyers has forced many publishers, and even first party studios, to shift to a broader release plan. Ultra restrictive partnerships with a console manufacturer don’t make as much sense because it cuts millions of end consumers out of the revenue stream. Even first party studios are targeting PC releases, save for a handful of exceptions (because not doing so leaves money on the table).
“Money-hatting” (assisting with development expenses) can’t cover the growing cost of these large teams, thus you see most of the large publishers distancing themselves from being paid for development, bonuses, or creating games for one platform.