Not OP, but I think there are two main reasons for this. Firstly if you are a professional you probably only had time to teach yourself what you needed for the job at hand. This is a great skill in and of itself but by definition it favors practice over theory. Secondly, if you're self-taught that means you didn't have a mentor and likely you don't know what you don't know. It's impossible to study topics you've never heard of, or whose connection to your field you're unaware of.