Why? Because 99.9999% of smartphone photos in real use (e.g. not in a review), give or take 100%, are of people. People move. Long exposures just lead to bad outcomes and blurred people.
I mean seriously search the net for Pixel 3 night mode. It's like the Suit Is Back. They're even using the same verbiage across them. And the uproarious nonsense about Google using AI to colourize is just...well a place like HN should just be chuckling at it.