I generally tell people because with any of the niche scents I wear, people get lost when you tell them. They want a quick and recognizable brand name their brain can lock on. Chanel, Dolce & Gabana; Armani. The designer fragrances for the most part very deliberately choose short, quick, easy names that work well in English. People tend to want your answer to contain at least something they can relate to and perhaps remember; either the designer or a simple evocative name like "Code," "Le Male," or "Gucci Pour Homme." I think they are delighted when they recognize some part of your answer.
But when you say "L'Instant de Guerlain Pour Homme," you can see their lights go out (especially if you impart a truly French pronunciation). Then you then have to assess whether or not they are really interested enough for you to repeat, go slowly, and truly let them know what it is ( "luh instant day gur-lain pour hommey) I've only ever had one person interested enough to have me write it down (I was wearing Domenico Caraceni 1913).
I find with the people I work with, when they ask the question it's more of a conversational question; they are not really interested in running out to purchase the scent. It's kind of an interesting social interaction really. I rotate through so many scents, I have no fears of others buying something I wear.
I don't think anyone I work with has even heard of Creed and they're probably the best known niche perfumer. Biggest concern I usually have when people ask is someone googling the scent and seeing the price, especially if I'm wearing a pricey scent (e.g. Antico Caruso). While many of the people I work with make more than me and could certainly afford pricey scents, most would find any men's fragrance purchase over about $80 to be a vain, frivolous and extravagant purchase. Most would be appalled that anyone who isn't a billionaire would pay over $200 for a scent.