@ James/NY....My 1987 trip to France (and Europe too) was the only time when I had to get a visa from the French Consulate in SF prior to going to France. It's on my US passport. Getting a visa before going to western Europe ie, France 1987, I've done it, likewise with commie Prague in 1973. Then I got the visa for the CSSR when I was in Paris, and in Sept 1977 for the CSSR again, I got that visa in Vienna.
To answer your question, I believe the reason (don't know if this is accurate as to why) was that US was ticked at Mitterrand since he refused US planes based in the UK permission to fly over French airspace on the way to bomb Libya for its role in putting a bomb on the US airliner that blew up flying over Scotland in 1986. Obviously, everyone on the plane died...horrific. In retaliation, France slapped a visa for US tourists going over to France in 1987. Visa or no visa I was going over anyway in the third week of July 1987. I don't remember how much I paid for it but do recall being inside the French Consulate among les français and waiting for the visa.
When I mentioned this visa requirement by the French government to a French professor who had taught in Calif as visiting exchange prof, she didn't think it was such a big deal and simply said to me, "You do that to us." I had forgotten that. True... she had to have an US visa to come to US as a normal, regular tourist, as did the west Germans I met in 1970s and '80s in SF.
When I went back to France again in the summer of 1989, the visa requirement had been dropped. The proof is in my passports then.