It is quite a bit different in robotics like this. Check out James Bruton on YT for a practical example of open source larger robotics. https://www.youtube.com/channel/UCUbDcUPed50Y_7KmfCXKohA

The motors used are almost always brushless because of the speeds accuracy and torque required. That means everything has software and electronics. This stuff gets very complicated fast. Most traditional auto makers are also outsourcing most of their software development and certainly not full stack or ground up oriented. This kind of thing needs to be designed from the start with every potential feature and future thing as part of the initial project. These types of things cannot be expanded easily. Like this is why China is actually good at EVs because they invested in building the whole thing from the bottom up the right way, instead of hack patching garbage and outsourcing.