"Almost everyone" kinda varies by what circles of people or community you're talking about. :P Smogon and Showdown, is yeah - primarily singles players. Did you know ALL official tournaments for Pokemon, and a considerable portion of ranked match players on X/Y cartridge play doubles though? I used to play singles actually ^^ Before I got into heavy deep and dirty metagame play hahah. I think as pokemon evolved forwards into the gens, becoming more and more competitive minded, singles became more and more broken, and less and less appealing to me. It's easier to exploit, less balanced in terms of what can be used and the amount of RNG independent as well as prediction independent factors that decide a match are much greater in Singles. There's some reasons they use doubles for all tournaments haha.