Yes, always be polite & courteous to people - why wouldn’t anyone want to be? But the root of this question is really a matter of perspective.
I’m going to assume the responses given thus far come from people who do NOT own private roads, rural lands, or tracts of private property. As someone who does - and as a country boy who was raised to respect private land ownership - I see this matter differently.
It is not required by me to post “private road” signs on any of the roads I own to maintain the road’s privacy status. It is not required by me to post “no trespassing” signs along the perimeter of the 50 private, wooded acres where I built my home to keep trespassers off of my land. It is not required of me to erect eyesore signs stating, “Private Beach” on my beaches, or doing anything to denote what is mine. At least not to ADULTS. Children...well, children are different. They NEED to be taught to respect what belongs to another. Adults are supposed to have already learned that lesson.
“Adults” have the responsibility to KNOW where they are, where they belong, and where they don’t belong. “Adults” are supposed to know if land is not owned by the State, is not owned by the Government, and is not owned by themselves, then it MUST be privately owned land. “Who” that private land owner happens to be is not a question - or even the business - for any trespasser to pose or even require proof of to understand they are trespassing.
This is basic stuff. This is not rocket science. And unless you truly would have NO problem with some stranger parking his car in your driveway, or a stranger going onto your yard to fly his drone from your land without your permission, doing anything else a stranger chooses to do on your property, or if you think you would actually enjoy having to PROVE you own your land, then this matter is not even up for debate.
I say this as a private landowner as well as a Native American, who cherishes his land ownership and who protects it. I’ve told more than one trespasser upon my lands, “Just because my yard is a lot bigger than yours does not mean my rights to privacy are smaller. The days of “discovering” and “exploring” other people’s land ended hundreds of years ago.”