A) Inspirational value. If somebody else on HN can make a useful tool to solve their problem in 3 hours, I might be inspired to take a crack at solving a probl

A) Inspirational value. If somebody else on HN can make a useful tool to solve their problem in 3 hours, I might be inspired to take a crack at solving a problem I've been putting off dealing with. B) Technical interest. HN isn't just about getting in to YC or proving you're a great entrepreneur; much of what we discuss is simply "interesting". Being assembled quickly is one attribute that can make something interesting. C) It helps us remember that not every problem is of the same scale, and not every solution has to be a multi-year startup-spawning VC-requiring system.