Funny thing is, IIRC, orcs are never really described physically in Tolkien, so, they could look like anything. But, savage race that sees in the dark, hates elves and wants to conquer the world is pretty darn close thematically.
It's kinda funny in a way when you think about it. D&D, purportedly, started out as a game to play in a S&S setting, rather than a high fantasy one like Tolkien. But, when D&D became very popular, likely the only fantasy that most players had read was high fantasy - in the late 70's, it wasn't easy to find S&S fantasy, or at least as easy as JRRT. Besides that, most players had likely read JRRT in school.
So, the game moves from a S&S pulp feel, into a more high fantasy one. We can see that easily in the move from Greyhawk, through Dragonlance and into Forgotten Realms. DL proved that high fantasy was a popular setting. Forgotten Realms simply moved with the trend.
Forward through the end of 1e and through the 2e days. High fantasy becomes the norm for most supplements. Sure, there are exceptions like Dark Sun, but, Forgotten Realms and a host of other settings remain solidly high fantasy.
Then the late 90's early oughts come. The market for reprint pulp fantasy has bloomed. S&S books and authors long out of print are suddenly popping up again. And people like it because they're bloody sick of high fantasy. And D&D follows right along. The whole "Back to the Dungeon" schtick is exactly that. Modules and settings come out that are very much riding on the resurfacing popularity of S&S fiction - Scarred Lands, Eberron, Freeport etc.
I imagine that ten years down the line, we'll see things swing back the other way again.
