There is some level of psychological attractiveness to making sure that all coins remain in circulation.

It's certainly possible to implement this: there would need to be consensus to ignore all blocks older than a certain number of blocks, as well as add unspent outputs in those blocks to the miner reward.

But it would create a very weird and irregular incentive for miners around the 100-year mark as some early blocks may cause thousands of coins to re-enter circulation. Even by today's standards these are enormous amounts.

So it may be preferable to simply consider them dead.