I've gotten them on occasion and I never even really thought about the ethical implications; I'm not sure it would be that bad? That said, I always suspect phishing whether it's real or a test and do not respond to them.
It really depends upon your industry and the cultural norms. My company doesn't even let vendors pay to cater the food when they visit. When I worked for a big for profit company, I loved when we'd have vendors pitch us stuff because they always catered lunch.