Housekeeper Nanny

I'm just curious, but why do Parents want a Nanny who also does house work?  I'm not one of those Nannies, however, when I look at job postings on various Sitter sites, I notice that almost every posting is for a Nanny or Sitter who also will do "housekeeping."  

Here's what I do in terms of cleaning: cleaning up after meals and snacks, if there's a mess made by the kids I'll vacuum, kids laundry, and occasionally, I'll unload the dishwasher.  I don't enjoy unloading it, but I'll do it once in awhile to help the Parents.  

But what annoys me is this one posting in Hoboken where the family needs school drop off and then have the person go back to their apartment to clean.  WHAT IS THAT?  Nannies are not slaves and anyone stupid enough to agree to that job is dumb.  It's one thing to clean up after the kids as a Nanny, but get a housekeeper if you need cleaning.