I mean Chrysler made 952,000'ish Jeep wranglers over its 10 year production run. That is a lot of parts to amortize tooling over. In order to reproduce all those many parts, you'd have to spend millions on tooling to even come close, and then you don't have the testing abilities of an OEM to prove your reverse engineering is valid. You would never recoup your costs. People piss and moan about 350 bucks for a radiator and that is the price after selling literally a million of them. Do you think you can make one that people will buy at a price they will pay?
The aftermarket companies, who specialize in producing reproductions can't get it right. Cars are so amazingly complex and highly engineered. I'm constantly in awe of how reliable and long lasting they actually are.