Tesla has a pretty vested interest in shit keeping working considering it's a pretty luxurious and high-profile product. The cut-price manufacturer of your $20 lightbulb or $300 fridge? Not so much.
The cheapest Chromebooks ship at $149 and have a pretty much unbrickable automated update flow that includes the firmware for the CPU and embedded controller(s).
It's not a matter of luxury, it's a matter of having people work on it who care.
Except when you're abroad on roaming cellular charges, and your three laptops decided that since your iPhone's personal hotspot is WiFi, it's time to download today's ChromeOS image version, because the one you had downloaded the night before was not good enough anymore.
Source: Chromebooks are awesome, and even with excesses like this, they're still the cheapest to operate by far.
Chrome OS tries to honor various DHCP server flags that state that the connection is metered. Unfortunately iOS doesn't seem to provide any such indication.
A comment in https://bugs.chromium.org/p/chromium/issues/detail?id=323010 claims that the BSSID is used for a "suspected" state, but that may not be enough to actually stop it from downloading updates, but I'm far from an expert in that domain.
In short, identifying tethering states with iOS seems to be hard.
You can determine whether the network is a Personal Hotspot heuristically. It is nice of them to have implemented private DHCP flags in Android, but if you routinely pull hundreds of megabytes without user interaction...
Then the opportunity is to convince customers why they should pay more for well-supported connected products. Easiest way is to make high-margin products.
That's the Tesla case. Or alternatively the Apple case. The vast majority of customers go with not that, and history shows you won't convince them the intangibles are worth it.
Tesla has a pretty vested interest in shit keeping working considering it's a pretty luxurious and high-profile product. The cut-price manufacturer of your $20 lightbulb or $300 fridge? Not so much.