Why do digital SLR (single lens reflex) cameras have shutters?

In analog days, the shutter let light in for some determinant time. That caused the film to be exposed for that duration. But in the digital age, why doesn’t “setting the shutter speed” just tell the internal computer how long it should record data from the sensor? What good does it do to actually open and close a physical shutter?

Just curious. And probably misinformed.

Categories: puzzles dw