This is called “knob and tube” wiring, and it was the standard before Romex. It’s actually quite safe if properly maintained. The wiring is secured around corners with ceramic “knobs”, and runs through joists are done through ceramic “tubes”. The reason is for expansion as the wiring heats up. Suspending it off the walls and in the tubes allows the wiring to expand and contract without chafing the insulation.
Modern Romex doesn’t expand as much because we use heavier gauges for the same current, and of course the insulation is a lot more durable, so we can just staple it to the studs. It still gets warm, but not as much. Romex was a big cost savings, mainly. It’s much easier (thus cheaper) to install.
Interestingly, the push is now to move to aluminum wiring, because the price of copper is through the roof. However aluminum expands a great deal more than copper under the same heat, so it has some special rules for installation that have to be followed. Improperly installed aluminum wiring has been the cause of a lot of electrical fires in modern houses. We’re kinda back to the problems that knob-and-tube solved.
