Isometrics?

Most sports movement require isometric stabilization of the core, so why are most core exercises centered around flexion, extension, and rotation? It's not that you can't create stability through these movements - of course you can, but isometric contractions are also very effective and underutiilzed tools.
Some core exercises that require isometric contraction include: sit-ups, the plank, suitcase deadlifts, one-arm farmer's walks, and Turkish get-ups. I hope I don't have to point out how great deadlifts and squats are at building an iron core...

Isometrics can be a highly effective tool in correcting glaring sticking points or for strength training individuals too weak to perform full range of motion exercises safely or effectively. A personal trainer friend of mine uses isometrics extensively during initial phases of training with detrained and elderly clients. I, personally, used isometrics almost exclusively for a period of time while I was learning how to perform a full range of motion Pistols.