different strokes for different folks.

I don't use one and have never had a problem with peep alignment. My friend however can't get his to align right because of his sub par strings so he is switching over to one.

I think another reason could be cosmetics. Alot of people are greatly influenced by what their bow looks like, and a loop of tubing at the top isn't as neat looking as a peep without it. Doesn't amount to a hill of beans, but could be another reason why some dont use it.

You make a good point about quality strings though. A LOT of new bows come with not so great strings. Like you said, a peep tube would eliminate the possible need for new strings. I, however, am about to place an order with Mr. Giblet for some bucknasty strings. Red and Black combo will look mighty sharp on my vectrix.