Denim stains on white saddle, saddle discolouration, dirty bums

if you see a bike with a perfectly white grip and white saddle, you can tell that he/she only ridden it for 5 minutes a day, or week even.

or they dont wear denim and do wear gloves or have very clean hands.

OR

the saddle and grips are new

OR

they clean their saddle and grips regularly

dont seen what difference it makes