Is it desirable, much less moral, for a percentage of the world's wealth to be in the hands of some early whales?
Imagine a system, where in every block, every miner could get one satoshi per 0.01 BTC on that address. In fact, there is no difference between a system with tail supply, and a system with fixed supply, where you can take someone's coins. Because that's what inflation is about: proportions. That's the only thing that matters. So, no hard forks are really needed to create a tail supply, you can instead force all users to pay a "tail supply fee", for example one satoshi per each 0.01 BTC. Then, miners could be forced by a soft-fork, to lock those "tail supply fees" to some future block number, just by using OP_CHECKLOCKTIMEVERIFY, to increase future block rewards.
And because it is something that can be solved by changing fee policy, no forks are needed to introduce that.
How would that even work technically? Coins whose keys have been lost cannot be moved...
You can always create a timelocked transaction, that could be mined after block number N. And then, you can publish it, then there are two options:
1) you will move your coins before block N, so the broadcasted version will be invalid
2) you will lose your keys, so after block N, miners will pick it (miners, if it will require no keys, but you can of course decide, what conditions are needed to take it)