Hi,
I would say this is the intuitive thing, otherwise it would simply be not consistent.
I have a constant histogram the moment curves is applied. You modify the Curve based on that. If the effect would be taken into the curve histogram, than it would mean the set curve should not affect the modified values and it would be a never ending loop. This is how curves just work and I really like that you can simply put another curves and check the new values.
Maybe what you want is an on-display updated histogram behind the current one on the same plot. But even so, it would still be confusing to "read" it. The curve line itself tells how the values are being modified.