There are definitely exceptions, that's true. Usually there's an interesting pharmacological reason why though.
For instance, SSRIs have this property, because for those drugs, the tolerance is the treatment effect. The tolerance has downstream effects on things like BDNF that are thought to be the true mechanism behind their efficacy. But this is also clear from the phenomenology observed, i.e people see improvements with a delayed effect.
This drug is very pharmacologically simple though. It's an extremely selective agonist for the 5-HT-4 receptor, and its effects are mostly acute, it seems(though due to a longish half-life it does take some time to reach steady-state with once daily dosing).
Now, I'm genuinely curious: does anyone know of a drug which,
1. Has acute psychoactive effects
2. Retains those effects under chronic same-dose usage
3. And the perceived effect can not be explained by correction of a rebound effect(i.e one cup of coffee in the morning might wake you up the same, but is it really, or is it just correcting an overly tired, mild withdrawal state associated with chronic use?).
I actually can't think of any.