That’s just the way Tamagotchi are designed and programmed. If you contact Bandai (depending if they still make Tamagotchi where you’re located) they might provided you with more information but it’s been this way on most modern releases.
Unfortunately, we can't act on this suggestion - TamaTalk is a fan-site, and isn't associated with Bandai, who created and manufactures the Tamagotchi toys.