When did the spider gene, and its characteristics become "Not Natural"? I don't recall the first spider coming about as a result of some test tube experiment... Nope, in fact it was captured from the wild... If humans didn't exist there would be a full breeding population of them in the wild right now...
And yes, people usually do produce morphs "because either they like the pattern or want the money." This is true for normals too. Your point?
If you actually owned and cared for spiders for years, and have bred them and their combinations for years, like many of us have, you might have a clue. But since you haven't, you don't have a clue. See how it works?
MANY people with hands on experience will tell you that spiders are often the best eaters in a collection. I can tell you for a fact that my top 3 eaters are all spiders or spider combos. So how exactly are you able to determine that the spider gene "definately isn't good or at all benefiting the animal?"
Like I said, you don't have a clue.