What is it with window Cleaners?

What is it with window Cleaners? Since our move, I have been trying to get a window cleaner.  I left umpteen messages on the answering machines but no reply for weeks.  All of a sudden, one week before Easter, they all started appearing at the door pleading for window cleaning jobs.  Why did they not respond to my messages and how did they know where I lived????!!! Anyway, I had to decline their services because I had just given the job to the one window cleaner who had the courtesy to respond immediately.

Maybe window Cleaners are like buses they all come at once!!!!!