I come from B/X and BECMI roots, so I've never really gotten why there need to be so many different mechanical differences between various elven subraces. I mean I get why they exist - Tolkien set the pattern and D&D took it up - but you can explain them all with setting fluff - they don't really need the crunch behind them. But of course people expect wood elves to have a different realization mechanically from high elves, and dark elves are very different from either, so you end up with all of these special cases.