Some cars hold alignment better than others. If the old tires showed even wear across the tread on all 4 wheels and there is no evidence of “cupping” then an alignment may not be necessary.
With numerous potholes hit per year an alignment is not a bad idea. If your last alignment was more than 2 years ago it is likely a good idea to get it done when you put on new tires.
An alignment is required whenever you replace front end suspension and steering parts. Some cars need 4 wheel alignments this includes AWD cars and those with independant rear suspension.