If Kureneko's treatment of the girls who asked her to go out for karaoke is any indication of how she acts towards her other classmates, then I sort of understand why no one would want to take the extra effort to be friendly\help her out. It's for that reason that I didn't feel too bad for when she was cleaning up alone. Not everyone is going to go out of their way to help someone who keeps putting up barriers. Only sandbag dude can deal with that "abuse" (I use the word abuse lightly considering this is not Kirino we're dealing with anymore.
)