Two possible reasons: 1) I think a lot of start-ups want to hire "smart" people. Because they expect the new person to eventually wear many hats. Objective-C, Java, Android, CSS, server side concurrency, monitoring. An we've all seen Hunter and Schmidt reference that tokenadult usually posts when talk about interviewing comes around and it does seem that a general mental ability test (like an IQ test) combined with a…
I think (1) is probably the primary reason, along with the fun factor I mentioned above. But honestly, why can't we just start giving IQ tests? Or at least asking for SAT scores? We shouldn't have to run through training puzzles just to prove we're smart enough to build a site.
I didn't have very good grades and my SATs were ok but not great, both primarily because I didn't study or apply myself. I was completely uninterested in school. Get me to write code and you'll see what I'm capable of. I'm certainly not unique in this regard.