This wasn't a registration issue. In CA, new car dealers immediately register cars upon sale. The issue is that license plates formerly weren't issued until sometime later, so it was legal to drive a new car for up to 6 months with no plates. That law was fixed as of 2019. Now dealers have to install temporary license plates.
https://www.dmv.ca.gov/portal/news-and-media/dmv-reminds-mot...
Steve Jobs was notorious for trading in his car every 6 months so that he could park in handicapped spaces without being ticketed.
https://abcnews.go.com/Technology/steve-jobs-car-apple-ceo-l...