Because laws are (mostly) a reflection of what society wants.
People are growingly concerned with both the car manu and Apple/Google control over their car and related extra software goodies.
Laws are really needed when businesses don’t play nicely. I don’t know the legal specifics, but I’m sure glad I don’t need to buy $1000’s of specialty tools to maintain my vehicle, and sure glad that replacement parts are readily available (and will be for decades).
Just image how much worse society would be if car manus did the same thing as Apple and had ID-paired parts. Sorry! Your AC doesn’t work anymore, please install a genuine Honda oil filter at your nearest Authorized Honda Shop, available for a minimum of $500.