Tires are not completely, perfectly round and can weigh more in some spots then in others, so when they are put on wheels, the complete wheel tire assembly is then balanced. If the tires are removed from the rims, and then replaced, they should be rebalanced, because there is no way to know if the tire is exactly in the same place it was before, on the rim.
As for alignment, I don't think you need to unless the steering or something else has been changed, and if it has been a long time since alignment, and if you have problems with the way the car handles. In other words, if you recently had it aligned, why do it again.?
When car shops rotate the tires on the car, they don't do an alignment each time.