Homer, The Odyssey, Penelope's problems with the suitors

Why didn't Penelope just kick the suitors out?  Why did she keep them hoping (and guessing)?  She obviously didn't want them there.  Was it because they wouldn't go unless she forced them out, and she had no way of forcing them?  OK, but that didn't mean that she had to keep feeding them and being nice to them, right?  Couldn't she at least ask their families to call them home?  Or was she afraid they or their families would do something bad to her if she wasn't hospitable?  Was there some kind of unspoken rule that said she had to entertain them? Or was she afraid she'd be forced into a marriage she didn't want if she dropped the pretense of choosing a suitable suitor?  But who would have forced her?  Or doesn't anyone really know?  Maybe we are so far away from that mentality that no one can understand their motives any more.  But I'd still like to find out if there is an explanation.