The garage can charge ridiculous amounts of money for trivial features and upgrades. Although the manufacturer may benefit from an App Store, the garage gets nothing.
Toyota, for example, charges something like $150 for a single satnav maps update, although now CarPlay/Android Auto is a standard feature and has tanked that market.
GM charges for access to key cloning and module programming/pairing. Its not overly expensive (~$40 per module), but super annoying and bug infested (software crashing/failing/constantly updating).
> GM charges for access to key cloning and module programming/pairing
A lot of this is done entirely in security by obscurity so there might not even be any actual cryptography/authentication involved. It's purely a rent-seeking operation.
Toyota, for example, charges something like $150 for a single satnav maps update, although now CarPlay/Android Auto is a standard feature and has tanked that market.