Thresholds are also useful for lighting dimmers, especially with LED and CFL elements. While the user might think they’re requesting 1%, the elements themselves might only be capable of much higher numbers. So having thresholds there help too. As in, sure, let the user request 1% dimming, but truncate that to the minimum level instead. User is happy, getting what they think they want, but not running into problems like LED drivers failing or the lights flashing.