Side mirrors cause a lot of drag (they take up perhaps 5% of total energy use). They could be replaced with cameras and a display inside the car, but haven't been, partly due to laws.

This resolves YES if a car without protruding mirrors is broadly, legally available in at least one EU country before 2027 and can drive on all public roads and highways.

https://www.wired.com/2014/04/tesla-auto-alliance-mirrors/

Why It’ll Be a While Before We Can Replace Car Mirrors With Cameras

Modern cars are essentially rolling computers, with chips and code controlling everything from your engine to your entertainment. The level of technology is so advanced that we may one day soon see drivers rendered irrelevant. And yet we’re still using small squares of reflective glass to see what’s…