iPhone 11 Pro Lower Volume Button Marks

[Darkhorse1]

I have noticed this issue on my iPhone 11 Pro and earlier on my iPhone X the lower volume button develops a mark on it over time that can't be wiped off, it's funny it only happens to the lower volume button and not the top volume button, any one else has this issue

 

[DevinNj]

I’ve never seen anyone with that before. Seems like something may be rubbing against the button possibly. I’m wondering if it’s from how you’re holding the phone. Or maybe from how you’re carrying it, like in your pockets or in a bag or a car mount? Just spitballing because you said your previous phone had the same thing.