How important are the skill levels when mapping?

When creating an own map and placing things (monsters, weapons, ammunition, ...) you can select which of them are there in the different skill levels (easy, medium, hard).

To be honest, I have neglected those options so far and in each skill level I have the same monsters, weapons and so on.

The only difference is then in "I'm too young to die" and "Nightmare", where the differences are based on damage the monsters make and number of ammunition in the clips because the engine does so, not the mapper.

"Hey, not too rough", "Hurt me plenty" and "Ultra-Violence" are basically the same in my maps.

So how important would you rate the different skills when mapping? Should I go through my maps and remove monsters for "Easy" and "Medium" or add some for "Hard"?

The more skill levels are implemented in your map, the wider audience might be able to beat your map.

There are a lot of folks here that only play certains difficulty levels like HMP or UV depending on how much skilled they are. If for example someone that only plays HMP gets killed multiple times and wants to lower the difficulty, the only difference will be a damage reduction and nothing else (more ammo if you go to ITYTD), which might frustrate that player and quit playing your map.

Have in mind that you can also play with the monster placement, like for example moving a chaingunner that is supposed to ambush the player from behind in UV and place it in the middle of the room so the player can spot him easily in lower difficulties, and place some extra ammo and health as well.

Personally, I would say it's always a good idea to implement difficulty settings on your maps (as it improves their accessibility thus giving you a wider player-base), unless one of the below is true:
(i) Your map is easy even on UV (like Fava Beans level of difficulty)

(ii) You are solely looking to appeal to expert doomers (like Sunder)

(iii) You are speedmapping to a heavy time constraint

Ok, sounds reasonable. I will take care of it.

Thank you!