system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are "Objects in mirror are closer than they appear"

May have been asked before but my gf and I were wondering last night. The passenger side mirror has that on it but not the drivers side. Why is that? Why wouldn't they make both mirrors the same as the drivers side?
gpt
Car mirrors with that sticker are deliberately made convex. The word convex means the mirror is not perfectly flat, it actually curves back towards the edges so that it if you put it down on a table mirror side down it would be slightly bowl-shaped. 

A convex mirror gives the driver a bigger field of view, because light bounces off the curve differently the farther from center it hits. So instead of the driver seeing just one lane of traffic in the mirror, they can see two lanes wide. This gives the driver more to see when they are deciding to change lanes, etc.

So why the passenger side but not the driver's side? Because the automakers believe that when a driver is looking on the driver's side, the driver needs to estimate distance between the car and other cars accurately, which is much more difficult with a convex mirror. The driver's side mirror is actually more crucial because a driver would have to turn their head far more to check behind without a mirror in a moment of sudden traffic changes, compared to the passenger side. In fact, for a long time there weren't side mirrors on the passenger sides of many cars, and then they added passenger side mirrors to the standard safety requirements.