This.
I do see where you are coming from. However, the rules are set down at the start of the season and every team plays knowing that outwith the top automatic promotion places (1st & 2nd down south, 1st in Scotland), you have to play a playoff round.
In England, it gives mid table teams something to play for rather than rendering 5 or 10 games meaningless. Less of an issue up here due to smaller leagues.
And if you don't like play offs, you'd have a field day with the Belgian or Argentine leagues and their crazy half seasons.