Totally agree, that's just basic workshop etiquette. Left a greasy palm sander on my bench once and it took ages to clean the gunk off. Drives you nuts when people treat shared tools like that.
Ugh, that's the worst. What goes through their heads when they do that? Like leaving a saw covered in wet sawdust. It rusts so fast. Do people just expect someone else to fix their mess? It ruins the tool for everyone.