I would think that it has a good bit to do with who is attending the games and the different pressure a young player feels because of that.
Having mainly mom and dad attend club games creates a certain emotion and atmosphere. Compare this to HS soccer/sports which has all of the players friends (probable romantic interests) and the weight of school pride and their street cred riding on the line. Hence there is possibly more pressure/reward from the HS environment - but usually with a lesser quality of play.
Just my thoughts.
