" ARE some of us just like magnets (like the Mommy having her kittens at YOUR place of work, and not another random address where they would not have been cared for?) or does it just seem that way because we are more aware of the cats, and so always notice them?"

I think some of us are magnets. I can't tell you how many times I made my husband stop for a stray dog (including a pitbull on the side of an expresway with a bag over it's head ) or how many mom & kittens ended up in my yard versus neighbors.
May sound silly to some, I think that animal's guardian angel guides them to us because we need to watch and care for them.