You see, I think that is the exact reason why most people don't care. People lump car seat fanatics in with the other mommy war issues and think it's just hyper dramatics. The difference being, giving your baby a bottle isn't going to rip their skull from their spine. In fact it's more than likely not going to hurt your kid at all. In fact, car seat safety is not even close to being comparable to the two issues you just mentioned. The more we can do to make people stop lumping it in with those other issues and start comparing it more to putting a life jacket on a kid who can't swim, or holding your toddlers hand in a busy parking lot, the sooner perception will change.I think you could ask this question about ANY parenting decision. It just happens that asking it here on car-seat.org makes it be about the best/safest car seats. If you asked on a breastfeeding forum, you'd get the same sort of discussion of why people don't breastfeed, and on a natural birth forum, why people don't have natural births, etc.
I wish I knew why people didn't try their hardest on any given topic, but they just don't. It's probably a very unique combination of experiences that makes any one person interested in one specific issue, so that you can't tease out any rhyme or reason. And I don't think that in most cases, it is global "not caring" or "not researching." As you can see, some parents obsess over germs but don't care about car safety.
P.s. I'm not suggesting that breastfeeding isn't an important issue, only that the importance pales in comparison to this topic.