Anyone can take the other side, if no players, the house will take the other side up to 25% of the pool. Just because the odds are in your favor doesn’t mean you will always win enough to justify the risk. If you bet 1000 sats on a heavy favorite, anyone who bets 100 sats on the other side can win your 1000 while you can only win their 100 sats. So the odds is baked in even though there is no spread.