why is that signal on how well they'll perform at the job? If someone doesn't code for fun but is a great programmer you don't want to hire them? Why is that considered acceptable?
Several times, people do very interesting personal projects, but fail to perform at the same level at work. That gives a clue that it may have been an unsuitable work environment that impeded their performance. It could also be a difference pertaining to their orientation to structured vs. unstructured working conditions. It could be related to explicit objectives with tight deadlines vs. exploratory development with open deadlines. And, more.
Knowing what my work environment is, I usually could understand their medium-to-long term fitness.
Hope this clarifies what I meant.
If yes, then the answer is: sometimes, depending on the other factors.