My Car wouldnt have AutoPark, Summon, Traffic Aware Cruise Control, Lane Assist, Spotify, Autopilot, 50 ekstra Horse Power and so on, without the software updates the connection to Big Brother provides. (Euro Spec S85D)
Your car could have all these features just as well without connection to Big Brother.
Just as I can get intelligent email sorting without using Inbox.
You can write your own software, or reverse and modify the official software.
In fact, you can even use third party software.
In an ideal future, cars would have a general API for the software, and you could use software for different things from different vendors.
Want to use the self-driving software from Google, but Apple Music? Sure!
Want to use the self-driving software from Mercedes, but Spotify and the navigation from Here.com? Sure!
You don’t see anyone sell or buy phones like that either – you can just switch the SIM and use it on another network.
If I want to use Apple Music, or Here navigation on my Tesla – instead of Spotify or the integrated navigation – why shouldn’t I be able to?
If I want to replace the firmware with my own (as long as it passes TÜV), why shouldn’t I be able to?
In fact, there are laws that specify I have to be able to disassemble and understand anything I buy, including any software. Any "you may not decompile" or "we will deactivate the car if you decompile the software" clauses are actually illegal in most of the EU.
Since all the hardware is controlled via a software firmware, they are able to tweak the voltage supply of each motor to decrease or increase output performance.
https://en.wikipedia.org/wiki/Engine_control_unit
Usually ECUs aren't updated online, but they can be updated by a dealer's computers.