I'd guess that a lot of devs it's not their main strength and their main concern is getting a working product out the door. If you're making "Bunnies go berserk" with the adventures of berserk rabbits as your main selling point, it seems unlikely that a smaller list of graphics fidelity options is going to dissuade anyone but the most hardcore graphics enthusiast from buying.

All those options are also going to need time allocated for a graphics developer to tune to suit your game if the out-of-the-box defaults aren't great, and as it's an area still in progress upgrading APIs and revalidating for your game on a range of hardware. If you're doing multiplatform with consoles/mobile that's even more in the mix, and you need to consider what will reward the time spent on it.