This happens quite often. A tire or tires is the culprit here. It generally happens with less expensive tires but not always.
When a tire is rotated it sometimes will put a tire on the steering axle (which also supports the most weight) that isn't true to the road. What I mean by that one side of the tire is pushing to the other. This will make your car drift left or right. It would not have been so noticeable on the rear axle which carries less load. An alignment isn't the problem, the tires are. If you try to align to correct a tire pull the next time you swap your tires it will pull again. This is why we take a car for a road test before and after every alignment. We see this happen with tires approximately in 20% of vehicles that come in for an alignment.