Most of those games really aren't worth $40. Very few mobile games are.
My guess is the assumption made was that owners of a brand new $250 handheld gaming device that essentially does nothing else (don't get me wrong; I've been using the pedometer to earn coins and having fun taking 3D photos, etc. but these are not worth $250) would be snapping up whatever (and by whatever, I do mean whatever) games were available upon release as is often the case with a new platform.
It's the standard pattern to try and sell half-baked or mediocre games when a platform debuts and at full MSRP ($40 for the 3DS this time). In this instance, it looks like not everyone is biting.
I'll buy RE:Mercenaries and MGS3-D but I really couldn't care less about most of the games currently available or even the majority of the games scheduled for release. Certainly not for $40.
