Are you guys talking about wraps or straps? I'll assume wraps since that is the topic title.
When I was into powerlifting I used wraps for squatting but only with max weights for singles. I never used them for working sets. I don't think it's a good idea to rely on them too much when you're trying to build up the squat. Your knees will be fine as long as your squatting technique is sound. Wraps are an artificial aid for the knee joint. You want the knee to be as strong as the rest of the leg and this won't happen if you use wraps all the time on leg exercises.
I still use wraps for my wrists when benching heavy because of the direct pressure they help alleviate. The use here though is completely different. The wraps in this case helps to immobilize the wrist joint. You don't want movement in the wrist as you would in the knee during a squat.
If we're talking about straps(grip aids) I never use them until my grip gives out on an exercise. They are a useful tool when the grip gives out but shouldn't be overused as this will hinder the development of grip strength. Hope this was helpful..