Same reason plenty of games end up just on one console+ PC.
What's has not happened is any type of confirmation that it is coming to PS4.
They're under a contract, they can't confirm it's coming to another console right now. It'd be stupid for them to not put it on another system when they're last title sold MORE on the other console. If it was exclusive forever, they'd say so but instead they specifically said "It's timed and it has a duration"
Respawn said it COULD come to other platforms.
It can, TF2 can. TF was confirmed later on to be a exclusive for full time.
Different wording but the same old shyt.
nikka ain't no different wording. They said it's timed and it has a duration. They're clear as day.
Idiot, all deals have a duration you can't write a contract without one. Which is why all devs say things like "anything is possible, it might end up on another platform. Hell insomniac said that ratchet and clank presumably could come to Xbox in the future. Should we be taking that as confirmation that R&C is coming to Xbox?

Insomniac would NEVER say it's coming to Xbox in the future because Ratchet and Clank is OWNED by Sony you fukking idiot, not Insomniac. Why the fukk would a non IP owner say another companies IP is possibly going to end up on Xbox?? Stop spewing misinformation you fukking nugget.
Like many other popular and non-popular video gaming companies, Insomniac Games, the developers and publishers of the Ratchet & Clankseries, does not actually own the franchise—Sony Computer Entertainment owns the Ratchet & Clank franchise. Because of this, their games are only published for PlayStation systems, meaning the PlayStation 2, PlayStation 3, PlayStation Portable, PlayStation Vita and soon, PlayStation 4.
http://ratchet.wikia.com/wiki/Sony_Computer_Entertainment
Them nikkas NEVER said that shyt you fukking jabroni.
Ratchet & Clank developer Insomniac Games is no different. And here's something you might not know about Insomniac: the studio owns virtually none of the iconic characters or worlds it's created. Not Ratchet, not Clank, not the world of Spyro the Dragon. That last one cuts especially deep considering the vast richesActivision's reaped from its Spyro-based Skylanders game. The former two are Sony-owned.
http://www.joystiq.com/2012/09/04/breaking-free-with-your-own-ip-insomniacs-ceo-on-whats-next/
In realty its not coming to PS4 until it actually is coming to PS4. Anything else is just wishful thinking from you Stans.
Just like some of you with Bloodborne and SFV.
Eat a dikk.