Anecdotal evidence - my sister had a 1st generation SRX sport-utility, and for whatever reason, Cadillac decided to put different tire widths on the front & rear wheels, with directional tread. This means you can't rotate the tires. It's also an all-wheel-drive model. So if you have an alignment issue that causes tire wear, or a puncture that can't be repaired, you can't just buy one tire -- you have to buy a full set of four at $200 (front) and $250 (rear) each.
Repair costs like that adds up quickly. Like the $1200 3rd row seat motor that died. She started calling it the thousand-dollar-car, since any repairs were around that price.
This is incredibly common among high-end luxury cars. The better handling that results from staggered wheel sizes is considered a luxury. The owner is assumed to be willing to shoulder a higher maintenance cost burden in return for a superior driving experience.
None of what you describe is unique to Cadillac -- this is what it is to own a luxury automobile. If it is not worth the price, don't buy one.
The Lexus SUVs that they have owned didn't do this. The tires for them were an odd size and usually had to be ordered, but all four wheels had the same size tire -- with standard (non-directional) tread. They still faced the "must replace all four" issue because of the full-time 4WD system, but at least they could be rotated to get full life out of them.
Which may be one reason why Lexus unexpectedly has a good total cost of ownership.
BTW, the Lexii had far fewer squeaks and rattles after 6 years than the Cadillac did, and had a much quieter ride overall.
To what benefit on their part? They don't manufacture tires, so they don't profit if you have to replace them more often.
As another commenter pointed out, this is quite common on performance and luxury vehicles because it has handling advantages. If you're buying a luxury car, you're by definition choosing to pay more than is absolutely necessary for (what you consider to be) a better experience. The tires are part of that. You can argue that the line should be drawn elsewhere, but it's not arbitrary, and it's very much in line with the market segment they're going after.
It's a SUV. They get used to tow boats, take science-fair projects to school, and take the family on vacations. They aren't used for track days at Road Atlanta.
Luxury vehicles (of which Cadillac is) I'll give you.
Performance vehicles I disagree. Handling choices are up to the mechanic/driver and you want to give them options but also make their maintenance choices simple. You should have a wide range of tire options on a performance car.
Repair costs like that adds up quickly. Like the $1200 3rd row seat motor that died. She started calling it the thousand-dollar-car, since any repairs were around that price.