Going beyond the obvious motive of child car seat manufacturers wanting to undermine the second-hand market, I expect design flaws could also play a part.
In case there is a flaw, e.g. poisons; unexpected decay of material strength; mold growth, then it's good to reduce the number of the old product around in case it's discovered, and a lawsuit manifests. Possibly the expiration could even mitigate damages in case of liability.
While superfluous product expiry is generally useful for selling more of any kind of product, a safety device for children is exactly the kind of product where mitigating liability from latent design flaws would be desirable for a manufacturer.
In case there is a flaw, e.g. poisons; unexpected decay of material strength; mold growth, then it's good to reduce the number of the old product around in case it's discovered, and a lawsuit manifests. Possibly the expiration could even mitigate damages in case of liability.
While superfluous product expiry is generally useful for selling more of any kind of product, a safety device for children is exactly the kind of product where mitigating liability from latent design flaws would be desirable for a manufacturer.