It's a matter of expectations. Working on my own projects, I can rewrite and ignore existing software to my heart's content. If I am working with others, there is a very strong expectation that 3rd party software will be used whenever possible, and that I will participate in other engineering practices/fads that are judged to be beneficial. I don't mind doing things that have a good rationale for the problem at hand, but very often a team will do X because X is supposed to be a good thing to do. Cargo cult engineering, if you will.