unittest and NIH

Phillip's defense of unittest seems spot on:

In short, there's very little reason to create a whole new testing framework; the one we have is just fine, even if its default features may not be to everybody's liking. But it's a framework, which means you're supposed to put something in it.... unittest deserves a lot more recognition than it gets, as it could be just the thing to stop us ending up with as many mutually-incompatible testing frameworks as we have mutually-incompatible web frameworks.

The same "not-invented-here" syndrome which underlies the cornucopia of Python web frameworks seems to drive the "reinvent unittest" meme. As others have noted, part of the problem may be that Python makes reinventing too easy: the marginal cost to learn somebody else's framework seems easy to beat by writing one's own.