I'm personally getting kind of sick of "it's not practical" as an excuse for why the general population has to suffer being poisoned and having their environment destroyed. Maybe we just don't need so many pilots and planes if it is so impractical to train and fly them?
We can't solve everything all at once. We're simply not that rich.
The reason leaded avgas isn't solved yet is because by itself it's a pretty small problem as far as things that are poisoning us and out planet go.
Obviously we're making progress, because people still care, but it's not getting resources in the same way that clean electrical energy is because it's a much smaller problem.
