Because most people, in the US don't even know how to drive a manual. Also manuals are not that hard to repair. Automatics, I think I might be able to replace the pan seal...maybe.
Here's something I pulled off the internet, so you know it's true.
"At last count just 3.9 percent of cars sold in U.S. were built with manual transmissions, but in the rest of the world, manual transmissions are still overwhelmingly the top choice. In Europe and Japan, for example more than 80 percent of cars sold have manual transmissions."
Heck, they even sell automatics for Harleys now.