Why protect personal data
You need to keep your electricity bill private, otherwise a thief would know exactly when you are at work or on vacation.
The shopping list is enough for a trained eye to tell who you vote for. Political organizations pay good money for knowing your affiliation and for being able to track how it changes over time. You can tell if someone's [wife is] pregnant just by the shopping list.
I can't find a good example for recipes, but someone will find a use for such information.
Using a password manager makes things simple, even the browser's built in "Remember password" provides more protection than no password.