Because people want to cheat so they can have a massive advantage. They can't use the default controller like everyone else cause they want things to be easy for them.
I was finally able to find me an Xbox Elite controller. Pretty nice and has some weight to it, not much, but definitely more than a standard controller. So, my experience so far on Halo 5 has been a nightmare. I started off with all the extra buttons which completely ruined my first few matches. I just mapped them to Jump and Dodge, so anytime I got into a "heated" situation, I was accidently jumping or dodging which just got me killed faster. So, at this point, I think I'm at a disadvantage, and like with either controller, I imagine as time goes on, I can only get better.
Nice thing though is you can detach the button actuators pretty easily, so I'm just down to 2 - 1 on each side. I like how their is a setting that changes the amount of pull to activate the main triggers. Also the extra joystick attachments are pretty neat too. I use the rounded one for my left stick, and the short indented one for the right one. Slowly but surely I'm getting used to the setup and getting better in matches...now, was it worth $150? hehehe I had the extra money, so I guess I'm happy so far.
No problems setting it down yet...I have an ottoman which is pretty firm. I do sometimes accidently trigger them when I go one handed to take a drink or pet the dog.