For a wiper, insufficient pressure will create smears and smudges on the windshield and affect visibility. A well designed aerodynamic blade minimally compensates the effects of wind lift but does not correct the lack of pressure on the wiper. This is because the washer fluid, rain or snow on the windshield act as a lubricant for the wipers. In extremely DRY conditions there is a slight difference in wiper motor effort. The difference isn' t critical.
Liquids act as lubricant.
All abrasive dirt is wiped off. Rust in an important life limiting factor in regular spring steel. Since it will not rust, it will keep its strength. Another important life-limiting factor of a spring is the number of cycles it will withstand. Failure generally occurs after one million cycles.