What is your favorite or memorable “solution to a mundane everyday problem” that turns out to have severely dystopian implications from sci-fi?

Just finished Dream Hotel, and one of the near-future devices is an implant that allows you to sleep a full cycle in only 5 hours. Other than the “work more” implication,

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agencies use dreams as evidence against a person, and later, to implant advertisements into dreams

Which then reminded me of appetite-suppressing toothpaste from The Outer Worlds. But instead of a weight-loss product,

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it is a necessity because the entire colony is starving

(I know smartphones etc. are at this point IRL, curious about more original ideas)