Matchmaking Question (Normals)

I play with a group of 5 from time to time. One of us isn't even level 30 yet and the rest of us are in silver. However within our past several games we've been matched against a team with at least 2 platinum or diamond ranked players. We get crushed every time this happens (as expected). Why does match making allow this? I don't want to say the games are not fun but its usually very one sided.