Actually, it doesn't really. If you've seen what manufacturers do to get some of those pretty glossy stain finishes, sometimes you might just be better off going with a wrap. I had some DW FinishPly drums, and for high-end drums, the wrap is actually that final layer to the finish. If the wrap is done correctly, meaning the entire things is glued down, then it becomes part of the shell and doesn't necessarily affect the resonance. If you were talking a cheaper Pearl Export or something where they apply the wrap, and tack it down over the seam, using the hardware to hold down the wrap, then that's bad. I've seen those wraps warp when left in the sun. But a properly glued down wrapped drum functions fine.