I don’t deny that this behaviour exists, but I don’t understand why it is allowed to exist. I understand it in the context of donating assets with a liquid mark

I don’t deny that this behaviour exists, but I don’t understand why it is allowed to exist. I understand it in the context of donating assets with a liquid market, like stocks and bonds, but for illiquid, difficult to value assets like these or art, it seems like a mega opportunity for tax evasion that could easily be cracked down upon. At least have a “claw back” where if the charity then sells the thing for $100,000 then the donor has to retract the full value of the original deduction.