My Van Van is 10 years old, spoked wheels, a lot of shiny bits and they are not know for their durable finish. I am not anal about cleaning it, if I get home and it's been cold and wet, I don't, I give it a good clean once a month. The bike looks newer than his 18 month old MT07. His last bike was a VFR800 (he never oiled the change on that either) I think it was about 15 years old, maybe more, I know it had fairings but the deterioration was nothing like the Yamaha which needs stripping down and restoring IMO.
It's a mystery. I am not a famous polisher but my current bike, a '95 Honda NTV650 which was in daily use until the current restrictions came in, looks better than many newer bikes. I've had it for 3 years. It came with a colour matched fairing. Previous to that I had 600 Bandit which was a nice bike but just didn't do it for me, so couldn't comment on paint durability as I sold it after a short time.
Before that I had another NTV650 which was in daily use, had it for 8 years, also put a fairing on it. It also didn't get a lot of cosmetic attention but cleaned up well when needed, no rust problems and looked pretty good when I came to sell it with 60 + thousand miles on it. No significant mechanical issues, tough as old boots etc. A proper old school Honda.
So bike manufacturers can produce a decently finished product if they want to.
I haven't had any real stinkers as far as paint finish is concerned though some were better than others.