In my opinion, its because manual is really a hassle to use for traffic jams and steep inclines. I know how to drive both tho but it was a nightmare to be stuck in traffic for a total of 5 hours in a day with manual and when the engine stalls when you make a mistake LOL! The second time i used a manual, i needed to use a manual for 100km due to my work.
Other than my first use of my manual in a driving test where i only had an hour of practice. i have no history of using or practicing a manual transmission in my life LOL. You will get used to it and the people who are honking their horns