The other players frequently spent the night at that Frat-house, so it wouldn't be just the DNA of the captains.
Early on the investigation when the reported the neighbor's complaints of noise, partying, urination... etc one said they have way too many people in that house - it violates some rule. Speculation was that the players sleeping over a lot made it seem like there was many players living there. 3 were on the lease, but 610 Buchanan was the hang out for the team.
Okay. But I doubt they showered there. Get drunk, pass out, go back to the dorm the next morning, shower, eat, go about the day's business. So, even if they hung out there, how likely is it that one pubic hair from Reade or Collin was there, and how likely is it that that one in a million chance pubic hair wound up in a pubic comb of Mangum's pubic area?