Because:
I’d only want a reverb
I don’t need lights as I have them already (and I don’t need a rear for MTB)
I don’t ever use mudguards
There are multiple options for pedals, and probably hundreds of different styles, all very particular to the user
The tyre sealant would probably have dried up by the time the bike had been exported/imported, and sold.
As it is, I prefer to build a bike from scratch. Complete bikes always come with crap bars, tyres, stems, saddles, BBs, brakes and headsets. I quite like the idea of buying a rolling chassis though. Klein used to do them, and call it a fuselage.