This perk is poorly designed when starting out (in fact, for most of the game).
As your raise your minimum, you get restricted on the range and power you can spend for things like breeding or casting alteration spells.
For example -
no points in the perk:
You have a range of 20-200 Power Balance to spend (so you can theoretically spend 180 if you leave a realm @ 200%)
20 points in the perk:
You have a range of 100-200 Power Balance to spend (you can only spend 100 if you leave a realm @ 200%)
This is, of course, is without other perks to increase your maximum. But those don’t arrive until much later.