5. in the case of Bundle in a Box, they started late, when a couple of bundles were established, well-known and popular already, and bundle fatigue was already kicking in, plus they cater to a niche of hardcore indie fans with a taste for experimental games and underdogs, instead of going for the "Top of the Pops" in indie gaming like e.g. HIB, so not only do they reach fewer people because they're not as well-known as the other bundles, their audience is also limited by their more courageous but also more risky approach regarding the choice of games.
They're kinda the indies of the indie bundle scene ;P
Personally I feel about them like I do about adventure game devs, even if I'm sometimes not that into the product, I almost feel obligated to support 'em being somewhat the target audience. Besides that though, they seem to be doing all the right things, sticking to indies, as You say actually digging out some lesser known stuff, DRM-free first and foremost, charity, and showcasing/supporting even more indies with the dev grant. And it's not like they're churning out new bundles every two weeks.
Speaking of the dev grant, I'm not that crazy about the current leader to be honest, Whispering Willows. Not that I've got anything against the game or the devs (that didn't come off right, I'm actually very much looking forward to the game), but they've had a successful Kickstarter
lately, raising 20k, so seems like maybe some other, smaller project could benefit more from the probably couple of hundred from the grant.
Oh, and as predicted, Kyttaro have lowered the "unlock levels" to 250 each: Unlocking the BIAB Cerebral Bundle Bonus Content