I got my R1T in June 2023 and since here are a few things they've improved, just off the top of my head, not bothering to look it up:
1. Significant improvement to ride quality via different / better suspension tuning.
2. Ability to schedule warming the cabin and pre-condition the battery
3. Completely redesigned the UX for setting drive modes and suspension height (for the better IMO)
4. Added a ton of car info, like battery temp, motor temp, and other info like altitude, various angles the vehicle is at (for off-roading), degrees the front wheels are turned
5. Added additional settings for ride softness / firmness (I got this update yesterday and haven't tried it yet)
When an update is ready I get a notification in the car and from the Rivian app on my phone. I can just hit apply and it installs it.
IMO a USB install would be a substantially worse experience and it would be much less likely that customers would actually install it.
But, for the type of person who just wants the car to stay the same as it was the day they bought it, and never change, it's not the vehicle for them. Personally I really like that it's continually improving and I don't have to go in for service or even go out to the truck to do an update.