I wouldnt be surprised if it's a hardware issue. It's the only reasonable explanation in a game they label as "social". Arcade Uno is more social than this game.
Look at it this way: Call of Duty (just chosen for the sake of an example here) has a chat that is automatically on for your team.
Destiny could have a chat that you can pop on for the current area instance with whatever the player limit is (16 like the Tower?)
I don't see that big of a difference
I've never come across a shooter where it wasnt on by default and every Halo game has had it. They could atleast have made it optional so there's soemthing going on. Perhaps they're worried about the Playstation players and MMO'ers, they're not used to voice communication and could easily be shocked.
To be honest I don't expect MMO players to be attracted to Destiny as an MMO which it doesn't really qualify as, with one of the main reasons actually being lack of communication options. If they do want to play it, however, having such an option would probably make it more attractive.
You seem to forget Halo is not the only game ever released when talking about "PlayStation players" not being used to voice communication >_>