A lot of it just weather being that damn good. It's almost become the next stealth rock.
I'm no fan of overcentralization, but the reasons that some things are used so much are valid. Take Ubers, where Kyogre, a Pokemon that is able to 2HKO every Pokemon in the game that doesn't have an immunity to Water, is used on half of all teams and any team that wants to get anywhere needs a dedicated counter to it.
Kyorge and Darkrai basically broke doubles, outside of clever choice scarfing. Zero skill to use.
Which has given me an odd affinity to Choice Band Sceptile and Primeape, because they both deal with those two almost perfectly. But even then I'll either have to make a risky switch or give something up to get Sceptile in a safe spot to Leaf Blade, since I don't lead with it.
If you want to see Creative, try Ubers. Steel Arceus with Cosmic Power, Mew baton passing not Nasty Plot or Swords Dance but Iron Defense and Amnesia, or
THUNDER WAVE GROUDON (I approve!) Really shows off all the game breakers Game Freak never considered, because, you know, they don't. Outside of Regigigas and Slaking where they deliberately build something amazing and neuter it with equal deliberation.
But after a while you'll wonder why you're playing anymore because of how overpowered everything is... of course you can say that about the 5th, and often the 4th, gen in general. Everything's gotten better, and too many things seem overpowered- but then I've been playing Ubers a lot lately.