If each team is given exactly a 50% chance, then how can a book lose? How can you win betting on 50% plays with -105 odds?
This could be due to books knowing public betting trends. If they know the public will take Vandy at -1, even though the true line could be +1, then why not? It's in their best interest to attract more money to the wrong side. The public "traps" themselves by overrating a team. It's not like the game is fixed and Celtics are given +30 points @home vs. the Heat.