Because I just had this experience... spot the spider, reach for the bugspray... start spraying... spider turns toward me and raise her front leg in attack position...
I'm usually perfectly fine with these little buddies:

Who anyway own the house, or their outside bros, covering the cars with their nightly webs (another "feature" of Toyohashi... mini-spiders are so all over the place that at first I thought the 'sandclock' Kamon was a reference to the black widow... making me call the city hall the castle of the spider...

But here, size and behaviour were quite... unsettling... and now I have to start post traumatic therapy for the cats who were of course beyond helpless...