Because it doesn't make any sense. Lets say you program nodes to enforce some criteria burred in a chain they're handed.  Great now I create a simulated history which that sets a bogus 'checkpoint' back early in the chain, but any _new_ nodes that attach to me I give this simulated history to before they know there is a better chain elsewhere and they start enforcing that rule and they are now forked off onto this bogus alternative chain; so you've introduced a vulnerability. Worse, because the forking off can be arbitrarily far back it becomes exponentially cheaper to do so long as hash-power is becoming exponentially cheaper.

This is even _before_ getting to the argument that what you're suggesting weakens the security model even if it works fine:  The result is that you give miners a new power, instead of just being able to reorder the history, they could also create arbitrary inflation just by adding new utxo to their updates. (which, if course, would be in all of their short-term interests to do)