Roads are among the worst conditions for corrosion. If you left your sink outside where it could be affected by salty sea spray, road salt or calcium chloride, with these chemicals sitting on the metal over time, it would also develop rust spots.

The Doha airport features a stainless steel roof; standard architectural stainless steel would be far too vulnerable to corrosion in this setting. They had to specify a duplex stainless steel with a special finish, and even so it requires regular cleaning and rust removal:

https://www.imoa.info/molybdenum-uses/molybdenum-grade-stain...

"Stainless steel" is only a relative term.