I never change the difficulty until FNV, I put it to very hard, first time I think I played ANY game and up the difficulty(In almost 20 years of gaming). FNV made me completely abandon the idea that you can go static(I know it was not totally static) in open world rpgs. You need scaling(not OB type, but FO3 type).
In theory though I see no issue with changing the diff if it makes the game more fun for you, a lot of games these days have "bypass" options if you get stuck in a level,etc which I think is great. I think quest markers should be the same way, in FNV there was usually enough info to complete the quest without them, but they were there as a "bypass option" if you got stuck. Unlike OB were there was not enough info to complete the quests without the markers, don't recall how it was in FO3.
I agree, and I don't see why anybody cares if someone turns down difficulty. It's a game, it's meant to be fun.
But I like to be forced into tense situations that require thinking and strategy. If you can headshot everything in 1-2 hits, than you just waltz through the game, and combat is just a cosmetic accessory rather than a feature. I played FNV on Very Hard/hardcoe with Arwen's Realism mod which made it harder, and still did 90% or more of the game without headgear, wearing leather armor that I chose because I thought it looked cool. But there were times where I had to withdraw and plan, and times that I didn't have enough ammo to finish a fight, or where I switched armor and put on headgear, and had to assess everything in my inventory because I needed every edge available. I love those moments.