It's more for convenience and little reminders where to look, landmarks, etc. Given most of us do not draw our own maps out, helps us not have to memorize everything.
I make my own excel maps, so I can use that for reference and item locations. Never played quests that had map function inside dungeons themselves yet. So for LBDX, even with no map function in this quest, I have my own map open anyway that shows where most everything is.
Yeah I remember you mentioning the Excel thing in the previous topic. You're quite exceptionally thorough like that.
Though, it's not to say that I haven't done my own series of screen-grabs and assembled some full map images myself, but I don't usually make custom notes beyond that.
Do you do that as a matter of habit with every quest you play, or is it just for ones you think are worth LPing?
Either way, for my own stuff, I always turn on spacebar maps in dungeons, or bonus areas, or checkpoints, or passages... or anything that's more than just a standard cave, honestly. Now that you mention it, I'm trying to think if I've seen dungeon maps in other quests... not that I've played a large amount... but I think there was one that had it. Can't remember it though.
Same concept with Slash. Used to playing with plain stab in the older quests. Now I'm so used to playing with Slash (in my top 3 favorite ZC things to have)
I'm beginning to get like that as well. I've always had a strong adherence to classic looks/gameplay when it comes to old games I've played for many years (including many others than just Zelda), but when a thing like that comes along... well, sometimes you just have to redefine the standard 
I've also become addicted to an anti-bump item that I got with a script from Avataro/Zoria, and if I ever did another quest (unlikely), that and slash would be coming right at the start.
Also on the subject of items, I thought it was funny what you mentioned in part 2, about using the ladder the way it was intended. I don't think I've seen a quest where you use the ladder to actually climb a wall rather than just cross a gap. That's a surprisingly novel idea in Hyrule, it would appear.