Sure, you can use whatever reason is appropriate to explain why there are so many elven subraces. But it boils down to (in your cases quite literally) "Word of God". There is no real, actual reason to exclude other races like orcs from more subrace options (like, those who really have different ways of living or physical qualities based on setting) or to simply not create a race at all (Undine, Merfolk) just to have another color coded elf. Besides marketing reasons, of course
Uh, and "word of god" is a bad idea in a fantasy game?

In my game it was a pair of wars involving lots of magic, chaos, and Elves who had essentially become gods. One war against a Demonic incursion followed by a civil war among the Elves (leading to the 4 Elvish sub-races; High Elf, Wood Elf, Sea Elf and Dark Elf). Thousands of years of war which nearly destroyed the world and magic well beyond the capability of "modern" magic.
Don't worry, I only have 3 Orc sub-races. Only 2 Goblin, because my Goblins are individually highly variable and tribes will sport different characteristics depending on their environment. 3 Dwarvish, 5 if you count Gnomes and Kobolds (degenerate Dwarves in my game). Oh, and Goblins (and Hobgoblins) are related to Elves. And Orcs to Humans. Then there are the Fey... and Centaurs and all those other "part of this, part of that" creatures. *sigh* It gets complex and less than PG. Arghh!!! And Giants and Dragons (my world started with only one type of each).
This explanation of diversity was the result of a long running (43 year old currently) campaign working to explain all the various sub races with a DM having degrees in history and cultural anthropology...
*edit* My Humans (not counting their racially diverged cousins, i.e. Orcs, and half breeds like Half Elves and Half Orcs, sport 3 main and a number of minor cultures, which differ in significant ways, but not physically.