Because, let's face it, your doubt is thirsty. It's like a plant that needs regular watering to stay healthy and not wither away into existential dread. Irrigating your doubt keeps it limber and ready for the next existential crisis.
Hazards of under/over-irrigation
Oh, please, for the love of all things sane, do not try to use a watering can or a sprinkler. That's just a recipe for disaster. We're not talking about plants here, we're talking about your fragile mental state. Use a specialized doubt irrigation system, like the one we've designed for you. It's like a miniature version of the Large Hadron Collider, but for your emotions.