Context kind of matters for me, but if I’m screwing any in, it’s both of them.
My monitors are on a swivel bar, and plug into the underside. Those get screwed completely in if the cable has screws. But on the desktop, since it doesn’t really move and I’ve never yanked a cable, they’re usually left loose.
There’s a famous example of one of these bulbs that’s been in operation since 1901
https://en.wikipedia.org/wiki/Centennial_Light