Laying -180 on a good team is one of the most common ways to slowly lose money. You can be right most of the time and still be flat.
The run line changes the math. You're getting a much better price to ask a slightly harder question: not just "does this team win," but "do they win by two."
When it works
Teams with real bullpens, playing tired opponents, in parks that don't suppress scoring. August is full of that — schedules compress and pitching staffs are stretched thin.
When it doesn't
Elite closers. If the opponent has one, the one-run game is exactly the game they're built to win, and your run line dies in the ninth.
This is a sample post — replace with your own take.