It's 100% not true that all programming jobs deal with trees. I worked for years on a major audio/video/screensharing communications SaaS product and never once needed to write recursive code or use a tree structure. Not all code is for processing data. There was tons of code that had very little to do with data structures or algorithms, and much more to do with implementing network protocols, business logic, managing state, abstracting the differences between the various operating systems we had to support, etc...