Ok:
'e' - see equipment, see traits, unequip WITHOUT swap
For melee without mweapon avoiding RL suicide, walk over lava so you don't damage your boots 'cause there's a Supercharge anyway, same for armor and minor enemies.
Very useful when micromanaging, unattainable through 'i' wtihout foregoing other advantages. Also good for access without 'w', 'W', 'T', 'P' and so forth.
'i' - see inventory (and relative room left, at a glance), use items(?), equip WITH swap
Well, why that's good's obvious. Too bad I wasn't aware of the swap earlier :) Does it make any practical game difference?
'u' - use items
I'd say the only duplication here's 'i' and 'u', if you can 'use' through 'i' (haven't tried).
Even then it's a convenient listing of your medkits.
As for Crawl and NetHack, they've very different mentalities. Here we don't worry about the BFG taking up space for our RL, CG, PR and CS combined, and can get a quick list of our worn equipment with a touch of the 'e', not 'I'>'foo*too much'. Who cares. I doubt anyone complains about weapon selections in Doom-like FPSs, and that's basically one 'i' away.
PS: doesn't ADoM have hundreds of strange, effectively useless commands...?