Some do that. Until recently people understood that you sat in a cafe or restaurant while you enjoyed your meal or coffee, and then left. If you did want to sit there talking with friends or reading you would leave if the place got crowded and customers stood around waiting for a table to free up. Now those unwritten conventions of behavior don't get learned, or some people actively ignore them.

I've seen staff politely ask people to leave to free up a table in the US, but in Asia staff frequently don't want to cause a confrontation, and may not speak English well enough to feel comfortable asking people to leave. So you see the staff in Thailand glancing nervously at the DNs hogging tables for hours, loudly talking on their phones, and getting away with it in a culture that mostly honors social conventions and avoids conflict.

They shouldn’t have to… people should have respect