Difficulty question

I've noticed that the difficulties I'm Too Young to Die and Hey, Not Too Rough are the exact same thing. So, why is there a I'm Too Young to Die difficulty?

Skill 1 in Doom, Heretic, and Hexen give out more ammo (I think twice the amount or 50% more).

Ichor is right; you get double ammo in I'm Too Young To Die (and in Nightmare):

// give double ammo in trainer mode, you'll need in nightmare
if (gameskill == sk_baby || gameskill == sk_nightmare)
  num <<= 1;

Furthermore, in I'm Too Young To Die, the damages you take are halved:

if (player && gameskill == sk_baby)
  damage >>= 1;   // take half damage in trainer mode

Code extracts both from p_inter.c

Oh yeah... I knew there was something else to it, but I just forgot what it was.