Splanations requested

I'm sure most of you have seen them, the mossy phoebe's nests that are built in the eaves of houses. I have googled and googled and cannot find an explanation for why they always build them right over the door. At my house, for instance, there is an extended expanse of eave with all the same features as the spot above the door, with the advantage of there not being a door there. And yet, they always seem to choose the spot through which humans and cats come and go. Why?