Or just up there with Beanie Babies as an investment vehicle

I live near a small airport with a lot of air traffic fueled by tetraethyl lead (avgas). So it seems society hasn't really caught up if it's a rich person's hobby.

I think the absestos and TEL lawsuits of the future will be settled in Bitcoin.

That is the EVM (Eth, Bsc, Matic) model (spend token as gas to pay for transactions). The EOS model requires staking tokens for CPU and Network, and you must buy RAM (which is account storage) on the open market.

You have described the economic model of smart contract platform cryptocurrencies.

Even Nakamoto chains work the same way, you require previous UTXOs (unspent transaction output) in order to pay the fee to spend them. Owning bitcoin is the right to spend it, and hopefully all the fees required in order to spend it.

Is Ethereum not this?

There might be some interesting applications, but wouldn't all those applications be fully out in the open, both code and data?

Zero-knowledge proofs and whitebox cryptography can probably help, but both are a far cry from general purpose computing / programming models.