In a world increasingly dominated by third party online multiplayer gaming on consoles, one of the most powerful motivating factors influencing the decisions of new console buyers is the "where my friends are playing"... it's the network effect.
Sony and Microsoft, however, are in different positions in the marketplace and thus are seeing two different equations as it relates to this effect.
Sony is leading console sales globally at greater than 2:1 for PS4s:XB1s.
This means that for every new consumer in the market for a new console, there's a >2/3 chance that said player has friends playing on PS4 and not XB1.
For Sony, "where my friends are playing" is more valuable, as it continually reinforced their lead in the marketplace.
For MS, giving up the less than 1/3 of buyers who are buying XB1 mainly because their friends all play on the platform is much easier. But on the other hand, for MS, giving up that minimal network advantage for the chance at killing Sony's network advantage outright with cross-play, is a much more valuable opportunity.
For Sony, given their market position, enabling cross-play to gain a little gamer goodwill would be hugely costly, as it would entirely invalidate their network advantage and one of the principal reasons that new console buyers are choosing PS4 over its competing platform.
We can argue all day about the gamer interests all we like, but Sony like MS is a business and so isn't looking to hand their direct competitor in the market a free ride, merely so that gamers can enjoy a bit of novelty.
Until, every single major games publisher is implementing cross-play between all willing platforms in all major new releases, to the exclusion of Sony, Sony will be unlikely to chance their policy on this. And in many ways we shouldn't blame them for looking out for their own corporate interests... as that's what companies exist to do.
If we're going to start complaining that companies should be putting their customer's interests above their corporate interests (something no successful company does ever), then why stop at cross-play? Why not get on at Sony, MS and Nintendo for not publishing their games on all platforms? After all, that's better for gamers; corporate interests be damned.
