The point, at least for me, isn't to punish long rest abusers, but to make the game more immersive and balanced for myself.
Right now, it is unclear how often Larian expects you to rest**. I can try to play reasonably, sleeping only when I think my characters would be tired, but there's no metric to measure that against except for how many resources I've used and that is entirely a player decision. It's similar to me being given a range of +0 to +5 weapons at the start of the game, and being told "the game is balanced for you using one of these options but we won't tell you which." Having to restrict my playstyle, intentionally choosing to play sub-optimally, is not fun (for non "challenge" runs) and is not good game design.
**That statement is actually a lie, because right now for story-purposes Larian expects you to rest after ~every combat to see all the cutscenes. However, this is not necessarily matched to the combat balance. Does Larian create encounters with the expectation that your party has full resources for each fight, or are they actually planning out encounters to account for attrition over an "adventuring day?" Who knows.
