I have one that wants tops only done., as she apparently does bottoms herself. I charged her the price for the whole house and got the job. Win win for me. I explained water would drop on bottom windows hoping I would get the whole house. So now I get paid full price for half the job....lol
Its also to do with the amount of window cleaners that come and go, better to stick with a crap cleaner than risk ending up with nobody, that said most people aren't really that bothered about perfection when it come tohaving their windows cleaned wfp is proof of that.