Mama didn’t raise no fool.  The kittens are getting taught by their mother to hang out right at the front door, since there’s always a chance that one of us will bring them something to eat.  Not that there are aren’t a zillion mice around in the fields and voles in the gardens, but the cats are opportunists and they’ll gladly accept handouts.  Having cats underfoot is an annoyance, but they are undeniably cute, so we don’t begrudge them their habit of obstructing the doorway.