Sports teams have difficulty in making ends meet in the vast majority of cases and there's no doubt, whatever anyone's feelings about them, that Playoffs get people through the turnstiles.
In an ideal world it would be the team that finishes top wins the championship, but we don't live in an ideal world.
If your team is 6th with a few matches to go then it keeps the interest up and more casual fans coming in. Plus, if you do make it, then potentially 2 extra home matches with bumper crowds.