not sure if Doom is the best example. I think for bragging rights, you could increase the difficulty. Or (in the 90s) when Doom was new, and you already replayed it on HurtMePlenty several times, and it became too easy, lets increase the difficulty and suddenly it felt fresh again.
But today? I don’t have time to replay Doom Eternal, so I play on HMP and it appears there is no reward for playing on harder difficulty, sadly.
A lot of racing games do reward you if you turn off assists with more XP or credits. Then I am actually willing to play above normal difficulty. Diablo 3 did it at some point, you could get better loot and more xp I think when you increased the difficulty. Nice!
I find it is always nice when a game does this. Or Agents of Mayhem. Make it harder, but your rookie agent will level up faster! It is so obvious, that this is a better system than one where “make it harder” only means it will be more stressful and nothing else.
The worst offender I think is Darkest Dungeon (a game I adore). There are so many options in the menu like play without corpses, radiant mode, and what not, I can’t even compare my play through with my buddies if I change a switch. Let me play how it is intended. I don’t touch any of the options, because I don’t know how they change the experience.