> What wiring?

If you've got normal residential power outlets, then you've got wiring inside the walls. Those wires are sized for the number of amps that the individual circuit's fuse or breaker allows, plus some limited safety margin.

Depending on hidden-in-the-wall details of how a circuit's wiring is run, and where you plug in panels and electrical loads, it might be quite easy to overload those wires - without blowing the fuse or tripping the breaker.

Overloaded wires can get very hot, and electrical fires starting inside walls really is a thing.

EDIT: Adding https://www.ul.com/insights/safety-considerations-plug-photo...