I have a lot of OEM Glock mags, and they are generally reliable and trouble free in all of my pistols, including a single 33rd OEM mag I have. I have been eyeballing the new 24 round ones, but have not read or heard much about if they have been reliable for folks that have tried them.
As for "why"... well, because. I've got a couple of the 21rd Magpul mags (which are a very handy size), and the 24's would fill the same niche (truck console).
Anyone have any first hand experience?