Privacy is what I gain, actually retain, by ignoring emails requesting if a domain name is for sale when that domain name is already listed for sale on a large domain name sales site.
My names for sale on a large site are under domain WHOIS privacy - the way I like things.
If somehow someone sleuthes out my old personal contact info for a name listed for sale on a name site they should then be aware the name is for sale!
Why I don't reply to a " is this name for sale inquiry is simple " ;
If I reply to the sleuth then likely personal data can and will be scraped from my email address etc and subject me to unwanted lowball offers and numerous " offers to sell me great names similar to mine " .
I am private person without a sick attitude and, I have eaten very well in this life without answering annoying and obnoxious inquiries about " is domain name XXXXX for sale ? " when if you typed in the name you are taken to a for sale lander!
I choose to offer names for sale on a popular large site - so their availability for purchase is clearly known to anyone interested in the name.
As an aside, I also don't return unsolicited phone calls nor respond to unsolicited junk mail.