true, but breaking someone's leg is worth it, even if they get better, if you need to stop them right in this moment.
Even if you can get the EXP back later, in the moment, you are degraded, and if a good roleplayer, playing your character as if they were the person from a year ago, who in the blink of an eye found themself in the future. . . .I'd think that often that would be enough to toss a giant monkey wrench into the middle of a situation.
On the flip side, I have seen interesting angles come up. . .in brief version:
Hero A goes to work for Mentalist B
They get along fine, but at some point A realizes B is evil and they fight. . .B deletes A to back before they turned using various Mind Erosion spells.
This happens a number of times over a span of many years. . .then A has a "Restoration True" cast on them, and recovers all of the lost segments of their life, goes up a level from the combined lost memories and experience returning, and is really, REALLY pissed off.
If playing with a group of good roleplayers, the ability to delete memories, even worse selectively delete them or change them, can have wide ranging and dramatic effects. . .and even if it does take 19/30th level magic to fix it, when it gets fixed it's usually quite good story watching the results of that unfold.