I have had my fair share of close encounters with moose when fully camoed and went un noticed. I'm a positive they either didn't notice me or didn't see me as a threat, even when staring right at me within bow range. Sure you can get animals with out it but if you are able to get just one more in your life time Because you blended into your surroundings wearing camo it is worth it to me. Bow hunting where close is a must it's only logical that being able to blend in will give you an edge at some point
I have had plenty of bow range encounters with deer without wearing camo. I have no doubt that good camo will improve your odds of not being made when caught out in the open, but you can get plenty close if you can break your silhouette with the terrain/vegetation and mind the wind. Really it is about the basics as was said above, even good camo won't help you if you can't keep still or are splashing your scent everywhere it shouldn't be.