Place oneself in a concert-hall and listen to where the sound are coming from,then one understand that two channels are a big compromize.
It depends on what you're trying to accomplish. If you want "you are there" so that you feel you're sitting in the Boston Symphony Hall then yes, you'll need more than 2 channels. However, if the idea is to put the Beatles in your living room, aka "they are here" then 2 channels should suffice. In that case you are simply recreating the 2D "stage" where they would be performing in your room.
Simply 2 different objectives in the recording and reproduction.
Ray