My decadent lifestyle of cortesans and exotic pets soaks up the hp first.
The spell works on fodder and significantly worn down opponents. It struggles with some 1/4 CR and many 1/2 CR opponents, and even some higher hp CR 1/8 beasts. 5e uses hp restrictions as an alternative to saves as also demonstrated in power word spells, and just like those spells it typically ends up being more restrictive than a saving throw.
It doesn't work on undead, beings immune to charm, or anything immune to sleep effects on top of the hp threshold.
The only thing the OP's premise shows is that it's useful under the right circumstances. It's decent against weak targets at low level and becomes niche fast.