alt Hacker NewsLeaded gasoline for cars started phasing out 52 years ago. It was fully banned 30 years ago. If there was any urgency behind getting rid of leaded avgas it would have been gone in that timeframe.
The FAA started looking at it 14 years ago. They planned to finish phasing it out in 2023. Three years after that, leaded avgas remains ubiquitous, and there's a plan to finish phasing it out in six years. (The 2030 date excludes Alaska, which is planned for 2032.) That's not what urgency looks like.
Cars don't need high octane fuel, aircraft do. Outside of the absolute smallest aircraft, you can't get enough power out of automobile gasoline.
They started looking at it 14 years ago, but there's been tons of bureaucratic roadblocks that have impeded progress. (Depending on who you ask, the petroleum companies were responsible for some of these.)
Even today, there are reports that the new unleaded avgas formulations cause engine damage, and we don't entirely know why that's happening. So there's still technical issues to work out. (But it's important, so folks are trying to solve them as quickly as possible.)