Tesla's lack of buttons long pre-dates any sort of ADAS feature development. Here's the interior from their 2009 Model S prototype:
https://i.redd.it/ahxh0bmh7ka11.jpg
The first version of autopilot that did anything that could charitably be called navigation wasn't introduced for another 8 years after this car and actual self-driving remains a distant goal 17 years later.
As far as I remember, Tesla has been talking about full self driving and auto-updates since before 2009, and although cameras weren't placed on the car until years later I would argue these early models were low enough production they were selling the idea more than the product (like how a sports car might be stylized after a jet, even though it doesn't contain a jet engine, but just to capture the feeling of something that's fast). It's also worth noting that car had a lot more buttons, including PRNDL, stock, and I believe AC/heater.
Also my Tesla drives me to work every day just fine without intervention. I don't think you need unsupervised full self driving for the screen to make sense, and while I didn't have a Tesla 11 years ago I think the vision was clear and a screen with minimal/no buttons was still useful. My point is just that if you're trying to make a so-called driver's car, without regular updates or meaningful self driving capabilities, it makes sense to add buttons so people know where things are while driving. The screen was a logical derivation from the other features tesla was building and incorporating, starting with the screen because it's easy is a mistake by companies like VW/benz/etc in my opinion.
I think the constant OTA updates was an intentional marketing point though (gotta spin the fact you’re selling it before it’s done)
And that Tesla has gear shifter, turn signals, etc. Tesla only went full FU about 2y ago