That's because it doesn't take much power to charge a nearly-charged battery, while it takes quite a lot of power to run a compressor, or, more fundamentally, to cool the interior of the vehicle on a hot day. If you had enough Peltier devices to cool the inside, it would draw a hell of a lot more current than trickle-charging a nearly-fully-charged battery - and that would increase the torque necessary to turn the alternator by a corresponding amount.
A mid-sized car has about a 3 ton AC. That is about the size that is used in the average house.
Something like a Cadillac Escalade probably has a 5 ton unit.
That's a lot of cooling and I don't see these chips cooling an SUV sitting in the sun in the South on a summer day.