You'd be surprised. I got into corporate video simply to transfer old video shot on VHS to DVD. As word traveled that this service was available, more people wanted video. So we bought a new camera. Now I needed better gear.
In terms of editing, I went from basic 2-track (one video, one sound) to doing more complex projects. One day I got asked to record a retirement. It was the first time I had a moving camera, multiple shots, complex scene editing, color correction, titling, a soundtrack, etc. Then I had to produce a DVD with a nice menu structure, etc. I learned enough doing that project to finally put my short documentary into the editor. Probably 3 dozen scenes, titles, sound, interviews (still need to be shot), background shots (still need to be done), etc.
As you get more and more projects, you begin to stretch yourself. For my documentary, I actually shot a scene outside Grumanns Chinese Theatre in Hollywood. However, I forgot to white balance. That was my first real tricky use of color correction. On the same project, I used color correction and grading to get some looks I wanted, and to match some footage. Velocity envelopes to go into slow motion for short periods, etc. Again, the project dictated learning new things.