I know I shouldn't, but the reasons I shouldn't are the reasons I do.
I love having to look in the DMG for how many spells a MU gets in his spell book to start with.
I love having to look under ability scores to find out if a Thief gets a bonus to xp and for what.
I love having to look at three different tables in two different books just to find out what my final thief ability scores will be.
I love how saving throws for PC's are in the DMG.
I love not knowing how many weapons a character starts with until I read a small buried chart near the equipment section.
I love that you can't find out what weapons your class can use by reading your class description.
It's so damned quirky and organizationally fucked up that to put together a character takes some skill, a skill which can only be learned after years of browsing the books as a kid, because who the heck has the time to do that now. Creating a character in AD&D is like a good romp down memory lane.