Summary: Bitcoin's security depends on exponentially decreasing block rewards being compensated by exponentially increasing transaction fees, but fee growth is constrained by the block size limit and user tolerance, creating an inevitable security budget crisis when Bitcoin's price growth inevitably slows from its current exponential trajectory.
At that point, say this century, the average transaction fee should be in the 100k sats range for miners to make collectively ~0.5% of what they're protecting yearly. Currently miners are making ~0.8% yearly.
The less profitable miners are, the easier it is to convince them for attacking the network. And this only gets more economically viable to achieve as time passes and there's a larger price with a smaller relative security budget.
Am I missing something? Are you comfortable with this?
References:
preciousblock
: a user-enforced checkpoint. I'd do this because the rewritten chain has no value to me. It arguably has no value to anyone I transact with either.