Well...both of my Mercs have had grotty or even unusable pins when I got them and needed replacements, you don't always get replacements with new pads
Stainless makes perfect sense if you're a 'fit & forget' type - warm salty water corrosion notwithstanding - there are plenty of grades of ss available
....oooh shiney...
http://www.pro-bolt.com/Products/0001000b000f003d
or even magnesium
!
Stainless cars - and even motorbikes! - have been tried, a big problem is weight