/diy/ - Do It Yourself

>>1566083
There isn't a reason. Having a GFCI is the only time I know of when you would do that, and even then, only on the GFCI outlet. It is not recommended to do that otherwise. If one outlet develops a fault then every outlet after it could go dead, depending on the fault. When using standard outlets you should have every outlet connected to the main run using a pigtail.

The only good reason to use both sets of screw terminals is when you want one outlet switched and the other not. In that, case you would sperate them by breaking the tab between each set of screws. Wire one set up to a switch and the other set up to the main run and there you go.

So, why was it done? 'Cause someone was a lazy fuck. Same reason I find outlets where they only grounded the metal box and not the outlet itself. It's faster and it works. It is not best practice.