Five seasons in now on The Walking Dead, it's hard to grow attached to new characters. A lot of older, core characters still exist and, much like one might actually experience in a zompocalypse, you grow to learn not to get too close to those you run into on the road. Bob's a good example. He was fine, but he perhaps hadn't been around long enough for most viewers to get close to. It's just the nature of the show's premise. We grow more callous and distrustful as time goes on. Unless it's a new enemy, our vitals don't usually spike.