Logic in brewing

When you brew a night vision potion in Minecraft, you can add fermented spider eye and create an invisibility potion. That doesn't seem right to me. Why do you get a positive potion effect out of adding fermented spider eye to another positive effect? My idea is to make two new potions. Potion of glowing brewed from glow berries (it will make them useable (imagine you play with friends and you get lost in a cave alone, you can both drink the glowing potion and find each other (SO COOL))) that can be inverted into a potion of invisibility AND potion of blindness, that you can brew with fermented spider eye from existing potion of night vision. We already can get those two effects in the game so why not add them like potions?