An interesting video

The other day i was watching a video from tabletop tactics, an old episode as I've only just come across their channel, featuring a tournament list. Now I've never played in a tournament before but it has been on my wish list as something to do. Now I know tournament lists are going to be slightly different to what I'm used to but this one was just silly.
So this list was a Tau and Eldar combined list. This in itself is fine in my book. Ok two powerful armies and the lists were aimed at utilising their strengths as well. All well and good so far, not what you'd want to face every game but what you've got to expect surely for a tournament. Now this is where it went wrong for me, the guy playing this army used the Eldar Farseer to summon daemons. Why??? Just why? This just doesn't fit into the 40K theme at all in my opinion. I just can't understand why this would happen from a narrative point of view. Yes it's a tournament list and they are trying to win but you've chosen to play a game with a rich and established background that you want to totally ignore. I just can't wrap my head around it. Now there maybe some fluff out there I don't know of where this has happened but it just seems so so odd to me.
While we're at it if you play Black Templars why not say I'm not going to use their Chapter tactics just so I can take a psyker. If you want a psyker and like the Templars colour scheme etc fine but call them your own chapter name however unimaginative it might end up being, just don't ignore a huge chunk of their history and rules just to get a psyker.
Hell why not go to the extreme and build a list where you go hey who cares about the Ultramarines nearly losing their home world to Tyranids let's ally them and while we're at it take a detachment of Chaos Space Marines painted as Word Bearers as it's not like they wouldn't be forgiven for what they did to Calth etc during the Horus Heresy. 
There are so many ways to play the game and use your imagination it's amazing and my rant isn't about saying you should never have an odd combination of forces. But at the end of the day you surely in part got into the game due to the background. So don't ignore it just to help you win. That's my opinion anyways.