system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why do some plugs have a wider and thinner prong, requiring you too insert the plug into the wall outlet in a specific way, and some plugs can be insert either way?

Is it a safety measure, and if so why are all plugs not required to be constructed this way? This question is specifically for American style outlets.
gpt
It is a safety measure.

The narrow blade connects to the *hot* side, while the wider blade connects to the *neutral* side.  The neutral wire in the outlet is very close to being the same voltage as ground, so if you accidentally touch the neutral wire, chances are nothing will happen.  Inside the appliance, the neutral side is used for those pieces where there's a greater chance of accidentally touching them.  For example, with a light socket, the socket itself should be connected to neutral while the contact all the way in the bottom of the socket should be connected to hot.

Some devices don't have any significant difference between the two lines internally, so there's no value in polarized plugs.