This is like saying "I've lived in a house for 15 years and I've never had a problem. I don't understand how people could have a problem living in a house." The thing is, living in a house isn't a very specific experience. The difficulty of the problems you might face varies a lot by many factors.
If I run into a problem I would research it, what is so bad about that? Even if I studied git source code in detail 15 years ago I would have forgotten it by now.
Do you know how to build a working computer from individual transistors or understand the physics behind it (I happen to know these things personally)? If not, better crack open your modern physics text and study particle in a box, along with the requisite differential equations, calculous and linear algebra just in case you might run into a problem one day.
