Yep...to capture those fleeting moments of better seeing. Last night was definitely proving a case for an even faster camera
You may be right in perfect seeing, but I've not experienced that here. I would suspect it would depend on individual camera specifications, notably sensitivity...with a more sensitive camera, you could capture better quality frames with usable gain and push the frame rates higher still.
My camera uploads raw data to the computer at ~50fps at that resolution, so the data isn't subject to compression.