A facebook friend of mine, Robert Archambeau, a very productive scholar, noted recently that advice on how to be productive is useless. What he said was "if you wanted to do it, you’d already be doing it, and if you don’t want to do it, you probably shouldn’t.” You have to kind of want to do it, because the external motivators are not that strong. There is no real fame in our profession, very little money or social prestige. The only external motivation is to get tenure, but that's just a way of keeping one's job, a job which requires us to keep publishing.
Outside of academia, the social standing of a professor is the same for a deadwood non-publisher as for a publishing star. It's even worse to be a productive scholar, in some cases. Every few years, I may or may not get some serious sign of how great I am, winning something major, etc... but I could go five or six years without anything like that as well. 15 or 20 colleagues at other universities might understand and appreciate my work. Some of those might think I'm ok but not really understand it too well. Others might think I have a name in the field but without having ever read me. That's really enough, though.
Once I got my first taste of being published I needed that from then on.
If you wanted to do it, you'd already be doing it. So if you're not, you have admit that either: you don't really want to, or: you do, in theory, but that it is low on your list. You can only write if you have watered all your plants, if everything else has been done.