All I can figure is that's by design. The process selects for some combination of IQ and how bad you want it, basically. If you can't or don't want to put in 10-15hrs a week prepping, for a few months, on top of your actual job (god knows nothing I actually do at work as a programmer helps me be better prepared for this kind of shit), to then subject yourself to a crushing marathon of a day, they don't want you. They have enough people who are willing to go through that, so they don't need to cater to those who aren't.

Probably one inherent benefit of a process this shitty, in addition to whatever benefits of the criteria they're selecting for, is that selected candidates identify more strongly with their co-workers and with the company than they otherwise would (see: Cialdini's Persuasion on the benefits of hazing)