The Apple Watch casing has proven to be pretty strong, but it's apparently normal for the various watch bands to become deformed, discolored, or scratched over time, according to Apple blog 9to5Mac.
Citing sources briefed on internal Apple support documents, 9to5Mac says Apple will not allow returns or replacements for watch bands that show normal wear and tear. This includes the discoloration of the leather bands "due to sweat or lotions," deformity of the fluoroeslastomer bands, and scratches and marks on the metal bands: Apple calls it all "expected behavior."
9to5Mac
Apple is likely trying to prevent another "gate" from happening to its products. The iPhone 4 suffered from "AntennaGate," which resulted in Apple providing free phone cases to all customers that requested one to help fix the cellular issues. More recently, the iPhone 6 and iPhone 6 Plus suffered from BendGate, in which the phone could be slightly deformed if they were sat on, or intentionally bent.
Financial implications aside, both "gates" cast shadows over these new products as critics and fans poked fun at these imperfections. Apple had to do a lot of marketing to help compensate: Steve Jobs called a press conference for AntennaGate, and the company invited journalists to tour its secret facilities that stress-tested the iPhone 6 during BendGate, in addition to a press release and offering replacements for bent phones.