Don't quote me as this being the primary reason of any kind of reason but someone I know who was writing a technical book with a publishing company said "You're

Don't quote me as this being the primary reason of any kind of reason but someone I know who was writing a technical book with a publishing company said "You're not paid to write books on just subjects that interests you, you get paid if there is market demand for that subject and the publishing company is willing to deal". I can't say for certain whether or not there is higher demand for Vi/Vim over Emacs or not but I am guessing base on the information provided above it has some factor to do with it if not entirely.