I don’t know when the RGB thing started or when it becomes so mainstream.
It began with having one or two components (probably peripherals) that had battery or status indicator lights on. Someone figured out that the lights looked better when stylised. Someone else figured out a way to offer different colours of light, to look better. Someone else figured out how to offer more lights, while someone else figured out how to change the lights and have different effects, while someone else turned the effects into patterns, before someone else found a way to have ALL the colours in all these different patterns, all while adopting this stuff from other walks of life (like under-counter and under-cupboard lighting in kitchens).
RGB has nothing to do with the functionality of the computer so not really the topic of discussion I want to raise in the thread. But nevertheless, expensive case with RGB short lived fashion statement.
I have Aquasuite - All my RGB components can be configured to reflect or indicate the status and conditions of anything my motherboard can detect or monitor through sensors - Hard drive and network activity, CPU and GPU temperatures, fan and pump speeds, media sound, flow rates, voltages, wattages, amperages, warning alarms... just about anything you can imagine, really.
It can be exceedingly functional, if you so desire!
Anyway, I really don’t mind subtle mood lighting but some cases are as some one said a light show from close encounter of the third kind.
That is purely subjective, though. What you consider a garish dress sense might pass for smart-casual in someone else's view.
It's also down to personal implementation. Most of my RGB is toned down, but I can whack up the brightness if I choose to have a light show. Many people can't be bothered with the tweaking, and the level of ******* around in things like i-Cue make it more like a full-time job!
Far easier to just leave everything set to the default Unicorn Puke demo mode.
under chassis lighting is quite cool I think, like under chassis lighting for cars.
Most RGB light shows are, in the minds of those people, as cool to them as your chavvy kevved-up car underlighting is to you.
But regarding your original point - When there's a £200,000 Bentley available with a V12 engine, all the bells and whistles and fully automated, that will always be the star of the show. Far fewer people will be interested in the £35,000 Bentley with a V4, plastic trim, cloth seats, no aircon, one bell, a very quiet whistle and only a 4-speed DSG gearbox.
Same with phones - People will starve themselves and kill each other to get the new Galaxy S20 Plus Ultra über-Note... but not the Galaxy A01.