I've had my alignment checked a few times and it's always been right but the first set of tyres I had on my car were down to the metal on the inside edge of the tyre after 9k. If I align my steering wheel dead straight then stand at the front of the car I can see the wheels point slightly away from each otherI've not had any problems with wear on this latest set of tyres though and they must be 4 or 5k old now.
I've done that aswell and by eye it does always look that way. I think its something to do with the shape of the arches and wheels.