Real clear what is going on here.
It’s a continuation cord. You see, the wiring works like this: The receptacle is split on both sides. The incoming power is double lugged on the bottom outlet. The outgoing power (to continue the circuit) is double lugged on the top outlet. You have to use the continuation cord to get the power from the bottom outlet to the top one.
Like I said, simple! /s
USA here: Or people saying “Don’t work overtime, they’ll just take it all in taxes”.
Well, my marginal tax rate on income has never been 100% (yet). While there are other factors to consider if you feel working overtime is worth it or not to you personally. That is not a valid logic to use.