Or at least a standard option?
I've been looking into a new car recently and have been really surprised that it's not even an option on the table for most cars I've looked at. It feels like it'd be a really good selling point - "you never had to worry about convincing insurance companies who's at fault!" and "if someone keys your car you might catch them on video!" the salesman will say, and it won't be entirely bullhonkey.
They could build them in with design in mind, hide the wires and device itself within the chassis, it would generally look a lot better than the after sales off brand options could ever look.
The quality of cameras has been good and cheap enough for years. They have huge bargaining power and the parts would cost them nothing, the biggest expensive would be in the design and production line changes and even then they'd be relatively minor tweaks.
Why isn't this a standard thing? Is there some big down side I'm missing?
Same reason as why A/C and electric Windows weren't standard features back in the mid 90s?