Excuses from Sony saying that they couldn't do it last year. Technically Ventrillo is kinda like Cross Game chat.
Who wants in game video chat? I don't want to see a 40 year old stroking himself to Call of Duty.
In game video chat, not that many people would use that, might be interesting but overall not wanted.
Cross game chat, TONS of people would use this and adore Sony for adding it.
With that being said Sony will probably add In game video chat.