How will sitting the top line hold them accountable for anything? If you believe that they aren't playing well because they aren't trying, then having them miss meaningless games at the tail end of a train wreck season is a reward, not a punishment. If anything they should play more.
If you truly believe they aren't trying, then they should be sent home for the year and shipped out in the off season. Just don't expect a good return because nobody wants a loser on their team.