You sort of already hit the nail on the head as to "why" - the Destiny population isn't actually that big, so adding in selectable gametypes just means they'd be splitting the population into smaller groups, increasing matchmaking times overall and having overall lower quality matches due to a smaller pool of players with varying skills, connection speeds, etc to choose from. If people think the matchmaking system is bad now, it'd only get worse this way. As much as I'd love to see some new gametypes like Big Team Battle, or Capture the Flag, or King of the Hill, or existing gametypes like Mayhem and IB have permanent spots in Crucible, I don't think it'll ever happen. The weird thing is, during the Halo years, I don't recall ever having issues finding games... No matter what time it was, even with lower populations in a certain gametype, it wasn't a problem... So, I'm really not sure what the holdup is on this with Bungie.

Agree. Back when Bungie was with Halo, the amount of game modes you choose from was unreal. Plus they had the tracker of how many thousands were playing at the time. Kinda dumb founded Destiny didn't implement that.