I think Pickles meant: Why would other members of the party risk their lives adventuring with someone who was a liability?
I think that it is difficult to justify actively bad characters, as no one would actually travel with them on dangerous missions. On the other hand, characters with flaws can be interesting. Sure, the fighter might be a bit clumsy, and not the strongest person around, but he's the one that's willing to go with you, and you need someone with his training.
I think the apparent loser works better in some systems than in others. It also makes a difference what you mean by apparent loser.
I created a grey elf wizard in 3.5 who started with a 20 int. His only other positive stat was a 12 con (my rule in 3.5 for RPGA characters was to always put 6 points into Con, then worry about where the rest of my stats should go), and his str was a 6. His father was a warrior/mage, and he grew up getting teased for his weak body, and always wanted to be a mighty warrior, but his body betrayed him. This didn't stop him from going into melee at the drop of a hat. At level 1, he went in with his dagger to help the rogue flank (and ended up killing the orc at 1d4-2 points of damage a round). At level 4, he jumped over a 10' pit trap set at the top of some stairs and took falling damage as he jumped off the stairs so that he could help the rogue flank an annis hag. In a later fight, the party paladin on his warhorse bull rushed him to get him away from the thick of the fighting.
I also played him as being an incorrigible librophile. He would read books while walking, while riding, while eating, etc. If he ran into books of Things Man Was Not Meant to Know (happened twice), he would read them. He once was in a battle in a library, and refused to use any spells that might harm the books. He routinely kept Scholar's Touch (instantly read a book) and Amanuensis (make copies of pages of text) prepared. Of course, he did his best to run away anytime he saw shadows (one of the few things he really feared).