There are substitutes that work in most engines. The others can be re-engined. Continuing to spray poison should not be in the table. But plane owners are rich and have money and time to lobby.
(I want nothing more than to be able to buy G100UL.)
Notice "not poisoning children" is not on their list of requirements. No, just that it doesn't cost you any money.
If I just took TEL and sprayed it over your house, I'd be arrested and have to pay tens of thousands for remediation. But do it in a plane? No problem!
You don't have to fly. You choose to poison us.