So why is the ranked system so unequalized?

When you win a ranked game you gain 14-21 LP normally. When you lose it's anywhere from loss prevented(which rarely happens) -16LP to about -26 LP?

Why is it so unequal? I just recently got demoted from S4 after being at 0LP for one loss only and then get instantly demoted to S5 after losing a game. How come sometimes it takes 3 games to get demoted to another tier? Example) S4 at 0LP loses 3 games then after 4th game loses and gets demoted to S5. So why is the system so messed up? Is it based on losses in a row? How does it work?