There's an old Chemistry joke, that I've reapplied to Software Engineering, and it goes something like:

A New Engineer (NE) shows up on their first day on the job, notebook in hand ready to learn. They get assigned to shadow an Experienced Engineer (EE) for their first day.

EE: Now, the thing is, for any project on our team, you only need to change about 3 lines of code. NE, preparing to write down notes: Which 3? EE: Well, it depends.

(Originally about Material Safety Data Sheets, and there only being 3 relevant lines on them).

I think this is what people miss about Software Development.