Correct me if I'm wrong:

When I take a picture, the sensor gather the light information "as a whole" during the exposition time and then saves it in the card. When I make a movie, the sensor scans line by line and then saves the frame in the card.

So, if this is correct, why the camera switch from global shutter (as in photo mode) to rolling shutter (movie mode) when filming?

Of course there must be a technical reason, but why bother using rolling shutter instead of global shutter, which is much more convenient?

Correct me if I'm wrong:

When I take a picture, the sensor gathers the light information "as a whole" during the exposure time and then saves it in the card. When I make a movie, the sensor scans line by line and then saves the frame in the card.

So, if this is correct, why does the camera switch from global shutter (as in photo mode) to rolling shutter (movie mode) when filming?

Of course there must be a technical reason, but why bother using a rolling shutter instead of a global shutter, which is much more convenient?