Like a 2 wire switch is that complicated? LOL. They already had them tooled for the Corvettes, and they NEEDED to run two wires to the light on those cars to ground the dome light even if they switched power. They didn't need to on the steel bodied cars and it goes against electrical design conventions for everything else.....where power is switched.
As many "relays/switches/electronics/connections/wiring etc." as I need to get the functions I want. My Nomad will have automatic on headlights, retained accessory power, and dome light soft dimming because I want those things. New cars have them and I like the features. And it's pretty simple to do with the DD module and the wiring isn't that complex. Plus I'll have a lot more "complicated" electrical things like EFI, keyless entry, fan control, electronic A/C control, power windows, power vent windows, power door locks, electric hood release, digital self-dimming mirror, and more. If you don't want those things stick to the simple stock stuff that you have the ability to wire and troubleshoot.
You keep drifting off-topic, which is WHY GM and others used switched ground to turn on dome lights. On a tri5 you save ONE connection by doing that. On a stock tri5 car you have one connection to each door switch, two connections to the dome light, and one to the headlight switch. That's a total of 5 connections. If you switched power you'd have one connection to the headlight switch ( if the switch was designed that way), two connections to each door, and one connection to the dome light for a total of 6. Getting one less connection while using more wire is hardly justification, imo, for changing the way the circuitry works for this one application. But maybe those push-on connectors were big bucks back then.