Too easy to scalp as the lines move throughout the week. They don't want you holding +125 when they know it will turn fav thus giving you +115 or so on the other side.
100% chance to make a profit with no chance of losing. IE 10 units on +125 (A), and then 10 units +115 (B)units. (A) wins you gain 2.5 units no matta what. B wins, you get 1.5 units no matta.
They have an inability to post a solid accurate line early in the week. The line will be refined by the time they post a moneyline so they won't get beat.