There are just too many common issues. Does Tesla regression test their updates?....or are they using us?
Agile programming's mantra is "fail fast, fail often." This is just meant as a means to develop iteratively. Programmers are able to deliver more value, faster, but sometimes it comes with risks. In order to develop iteratively, you can't boil the ocean and often times developers are tasked to code only the piece they're working on.
That's the short answer.
The long answer is more along the lines of, "what about the factory/assembly QA?" and "what are the inconsistencies between hardware?" These can be more difficult questions to answer. Legacy automakers delivered technology and features in a much slower pattern because:
1. They developed everything in-house. This meant starting over from scratch for nearly every piece of new tech that is sold.
2. Their feedback loop consisted of automotive sales. If a feature or vehicle didn't sell well (or the same of a competitor), it wasn't something worth investing in.
Tesla is a Beta company with a Beta product. Most of the software within the OS in our vehicles come with a bunch of warnings. I would like to know what the bare minimum of the vehicle can be operated on. If the screen is broken, can I still drive my car? If yes, for how long? Also, if the screen is broken, and I lose my keys or replace my phone, how do i fix that? Does that mean I have to spend $$$$ just to use my car?