What exactly is keeping us from making concrete with salt water, for things like sidewalks? In the northeast US, sidewalks frequently are in horrible condition

What exactly is keeping us from making concrete with salt water, for things like sidewalks? In the northeast US, sidewalks frequently are in horrible condition after only a few years, because of the salt used in the winter. Sidewalks do not use steel rebar; they're just simple poured concrete. So why can't they make them with a better mixture that doesn't corrode so easily? (I'm guessing the answer is: replacing them frequently makes a lot of money for some concrete company that the town mayor is friends with.)