Charlie,

People are "caught up" with evolution because it's an extremely well-established scientific theory. The hypothesis of Lamarckian evolution, of the sort you cited, is simply not how things work, which is why we disregard it. There was vigorous scientific debate on these competing hypotheses ... 100-150 years ago, but it is since settled.

I don't know if this was your intention, but I often hear arguments from evolution deniers that claim scientists are "caught up" with evolution, and simply haven't considered the alternatives. These arguments almost invariably come from non-scientists, and are absolutely incorrect.

As for the question evolutionary advantage of not having eyes; it's about economy, for one part. Making eyes takes energy. Maintaining the neural pathways necessary for vision takes energy as well, and uses valuable cranial space. And what does a salamander brain in a dark cave do with the sensory input from sight? It may not seem like much, but if two similar phenotypes are competing for survival/selection, and one is just a bit more energy efficient, it is the one likely to survive and propagate. Carry that for millions of years, and the probability turns into near certainty.