I lost count of how many times I had to explain a fresh graduate that no, I would not let them build their own compression library.
Inexperience engenders bold gratuitousness.
50% of all programmers, at any given time, have less than 5 years of experience (which follows from the fact that the number of programmers doubles every 5 years, as Uncle Bob explains here http://som.yale.edu/news/2014/09/uncle-bob-martin-speaks-yale-som)
This determines several peculiarities of all things digital, one of which is that the Not Invented Here syndrome is continuously fueled by inexperience.
The dimension of the phenomenon is equally evident in commercial products as in the open source world (which naturally harbors a large number of young, inexperienced practitioners). The result is the cacophony of duplicated, half-baked, short-lived, ill-conceived and not-up-to-scratch solutions which we have all become used to.
The NIH syndrome is thus endemic and characteristic of our field, and at least partially explains why one in a hundred startups, and, maybe, one in thousand open source projects, can justify their existence, and survive beyond the initial optimism.
It affects equally startup founders, digital agencies, young programmers, designers, and sometimes even large and established software companies that should know better than that. It’s the natural byproduct of growth and a constant state of gold rush mentality.