If you have never noted the fact that they are predicated upon evolution as a fact, you haven't read them with any sort of care.
susie
You don't believe that organisms evolved? That would make you a creo, wouldn't it?
Have you read equivalent textbooks in other fields to see their treatment? It seems the only criticism we see here is of biology texts. I suspect that criticism is based more on religious sensitivity to the results of evolutionary theory than actual approaches in biology texts as opposed to other fields, but it has been a while since I perused them, so...
By the way, evolution is both a fact and a theory. The fact part is that each generation is slightly different from the one before it. The theory part seeks to explain these differences, and their effects through time.