ELI5: Why are larger (house, car) rechargeable batteries specified in (k)Wh but smaller batteries (laptop, smartphone) are specified in (m)Ah?

I get that, for a house/solar battery, it sort of makes sense as your typical energy usage would be measured in kWh on your bills. For the smaller devices, though, the chargers are usually rated in watts (especially if it's USB-C), so why are the batteries specified in amp hours by the manufacturers?