Raven Crowking said:
Nitpick: Everything was optional in 1e. That was made quite clear in the 1e ruleset.
Err... no.
"most of what is found herein is essential to the campaign, and those sections which are not - such as subclasses of characters, psionics and similar material - are clearly labeled as optional for inclusion." - AD&D PH page 6.
There's also a lot of discussion about how games should be uniform as to the rules used. See also DMG page 7. Gygax expanded upon this in Dragon Magazine, going so far to say if you don't use the rules, you're not playing AD&D. (D&D was the set for tinkering; AD&D grew out of the fact that there were so many different versions of D&D being played - you couldn't take a PC from one game to another, everything would be different!).
"And while there are no optionals for the major systems of ADVANCED D&D (for uniformity of rules and procedures from game to game, campagin to campaign, is stressed), there are plenty of areas where your own creativity and imagination are not bounded by the parameters of the game system." - AD&D DMG 9
In the PHB, the only optional material are Psionics (appendix i), and Bards (appendix ii). They're clearly marked as optional; nothing else is.
In the DMG, the DM has the choice of what ability score generation system is used (page 11). Secondary skills are optional.
The DMG (in the Afterword) exhorts the DM to "hew the line with respect to conformity to major systems and uniformity of play in general". The intent of that afterword is to allow the DM to override bits of the rulebook that are obviously written by Gary on a bad day.

But the rules aren't optional by default.
Cheers!