Two very different problems, though both are locks. In the case of a car you don't always get to choose the security of the community it lives in. Its portability, price and effective lifespan dictate different standards of security.
In the US the average length of car ownership is at an all time high of 6 years. You can reasonably expect the locks to outlive your interest in the vehicle. Whereas (and this is all quick googling to get to a point, so anyone feel free to correct my figures) the average ownership of a home is 20 years. Now, while locks can certainly survive that long, it's a good idea to replace them once in a while.
Additionally, in the rental market where turnover is significantly higher, there are often laws that require the regular changing of the locks from tenant to tenant.
And - another factor - insurance standards related to security on cars are much more robust than insurance related to security on buildings. You can occasionally find a break for having a second lock, or deadbolt, etc. but your returns on insurance breaks diminish completely as you invest in higher end physical security.
All of this is to say - door locks are a commoditized after-market product that are influenced by geography. They are made to be replaced/maintained by the user and there will always be a thriving budget marketplace for them. Your car locks, on the other hand, are never meant to be worked on by the user, are rarely replaced and have almost no competitive after-market.
Hope that helps lay out some of the differences between the two.
(and I could go on. Lot of other stuff around OEM, cost of production, ability to sell on security, etc. etc.)
They're expensive, complicated, failure-prone and proprietary. But then again, so are some high-security door locks.
Honestly it's probably just the industry wants to keep its separate businesses which adds up to more money. People sell rfid fobs separate from their high-security keys while cars combine the two. There's no reason you couldn't take the ECU out of a Lexus, wire it up to an arduino, plug it into a wall, attach a solenoid to a door lock and weld the lock cylinder of the car into a door handle. Since modern Lexus keys act as RFIDs when their batteries die it should be mostly fail proof.
Or just use a better lock. Pin-tumbler locks are just awful and inexcusable. We have know that they are bad and had better options for more than 5 decades. Yet for some strange reason they have managed to maintain their market dominance in the US. Every year they add new mitigation features that generally either don't actually work, or if they work, they just make picking it a tiny bit harder. If you want your front door not to be easily pickable, just get Abloy Protec or a similar lock for it.
Of course, the reason for this is that criminals largely don't pick locks.
