because the corrosion of metal in contact with water. also water don't have a good lubricate factor so it can't use in some application.

The boiling point is too low, and it is a corrosive. See the Grande Canyon for more details.

it boiling point is too low compared to oil so it evaporates fast and it causes rust

It also doesn't work very well when it is frozen.

Add -it is less viscous