Some cars are easier on tires, some are harder
If you drive a Twin I Beam Ford, rotations are mandatory.
If you drive a Festiva with 12" wheels, I doubt it will care what you do with the tires
All Wheel Drive cars can act up if you do not keep the tires properly rotated and inflated. Some AWD systems are so sensitive that tires being just slightly different sizes from improper rotation or inflation will cause malfunction or damage to the AWD system.
Also, not everyone can afford to drive a brand new car. Some of us are stuck with older cars with more "seasoned" suspension parts, that still may work, but are a little harder on our tires. Our older shock absorbers cause very slight cupping in the tires, our allignments toe may not be dead on perfect and the tires could feather some, and some sloppy tired ball joints or cracking aged control arm bushings could cause that inner edge to really get rough on the tire. If left un-rotated, the tires would become square shaped on these cars and it would feel like riding a school bus over a gravel pit. But if rotated, the tires could live happily ever after and you can continue riding in style in your couch on wheels.
And seriously, just buy your tires at a place that offers free rotations. I drop mine off, walk across the street and eat lunch, and its done when I'm done eating.