Because you're looking at it from a consumer stand point in which things should never change. Developers scrap ideas because you have to take a spear balance it, model it, texture it, animate it, give it unique skills and different versions only to have it play slightly different than a two handed sword. At that point is it worth it?
If that was true all swords in the game would be a steel longsword that changes its stats as you level up, whats the point in coding a different appearance and coming up with a new name?
They have to make a deadline and is it really worth it to add spears when they're not all that unique.
If it was just recoding and retestexturing a longsword as you said it wouldn't really take much work at all.
One could argue that they should have pushed back the release but I'd argue that a game is never finished. Ask a artists if they ever feel a piece is finished or perfect and they'll more often then not say that it isn't. Deadlines are given because when this is your craft you'll spend hours tweaking and fine tuning it never actually getting to your end goal of completion.
Deadlines should also be chosen based on the time estimated to get all the features in and flesh out the world, not because 11/11/11 is a cool release date.
That aside I hate this idea of "dumbing" down the game. It's insulting and pretentious to assume that a mass audience couldn't enjoy your ideal version of a game. It's as if you cannot move on from the stone age and still use maps because they're so much more detailed than a GPS which is just a dumbed down version of a map.
On the contrary I think the mass audience could enjoy my idea of an ideal game, Bethesda doesn't.
And a GPS has all the features of a map and more unlike Skyrim which has taken a few features out and improved on others, it's pretentious to assume anyone who enjoyed Morrowind more is just nostalgic and wants to play Morrowind with better graphics.
Times change, games change. Yes, it probably would be nice for some people to have something from an earlier release in a game, but in all reality how many people who played those original release games are actually still here today? I would suggest that in comparison to the number of copies of the game sold that the figure is very low.
I played Daggerfall close to the original release, and the only reason there is more fans of newer games over older ones here is because instead of making games in the mould of Daggerfall and letting their fanbase grow they made a game that would appeal to a large fan base that already exsisted.