Sounds like someone saw the new Second Son commercial. Am I right? Lol.
I dunno. I think commercials and trailers are two separate things, with slightly different purposes. Something like a live-action TV commercial is simply made to get attention, and the live action aspect of it helps to appeal to a broader audience (namely, non-gamers). It just puts the word out there that Game X exists (or will in the near future), leaving it up to the viewers to say, "Hey, this looks interesting. I should try to find out more about it." From there, full trailers and the like can be looked up for more details on the game.
It's not like they exclusively make these kinds of commercials, with no other form of promotion of new games' features and whatnot. Trailers, interviews, gameplay footage, etc. are released for the purpose of informing those interested of what they can expect from the games, and in most cases, there are plenty of them released in due time. Commercials are just an entry point to lead people to the other information.