Having no real value or use, in this case, its used to extremely express your perpetual disapproval towards someone who is not in the same cultural sub-group.
When your classmate says they have not watched The Lord of the Rings trilogy and with posh disapproval, you respond with nothing but the word Worthless.
Sue: did Shy Guy ask you to the dance?
Hailey: nope he didn't go out on a limb for me. he asked Ugly Betty :'( cuz don't you know? I am not worth it.
Sue: is NOT worthless! (hug)
Hailey: lo1 thanks.i know Shy Guy is the wrong guy for me- and last night Brave Dave asked me and yep Im going and i don't care if it hurts Shy Betty. they can have each other i hope they have lots of ugly babies.