If I hear the word "useless" one more time...

Me and Jo recently have been butting heads over some things in my flagship DnD 4.0 game. Mainly the topic of usefullness, and what constituted a useful player. Apparently by her definition of Useless, if you are anything of small size and are not the living personification, an Avatar even, of one if not all the Core Classifications of a RPG Party team lineup (Melee, Magic, Stealth, Diplomacy), you have no business being there. It's the cool kids table, and only tall badasses get to sit at the cool kids table.

I always was of the mind that usefullness and uselessness were all situational rather than being a racial/class thing.
A rogue with a low lockpicking skill can be considered useless.
A fighter in a lineup of five other fighters of all possible builds can be perceived as useless.
The cleric that doesn't heal his companions during combat is definitely useless.
An Evil Aligned character in a group of Good and Lawful Good characters is useless for anything except getting everyone else in trouble.
A character with low strength but high dex who insists on going melee is useless.
The character who insists on being the diplomat and has shit for charisma is useless.
A Dwarf that doesn't drink isn't useless per se, but is just really really wrong.

I'm not too sure if I'm the only one with a group where the sudden desire to be "useful" and "needed" has become such necessary terms of character creation. I know where it began, for sure. During a Star Wars game set in a military setting, one of my players wanted to play the role of Medic, which started a discussion over what role each player served. This stuck, so now instead of character they want to play, they roll the character they feel they should play. And I find it annoying.
Granted, I don't accept every character idea that hits my desk. However if someone comes to me and says "This is the character I want to play", I will certainly listen, and suggest on how best to make it work. Even if it's the Corgi Race and stats I put up on my facebook, or a Frogman warrior. I don't look for usefullness as a DM, I look for creativity.

Maybe that's where I fail?