Why Rothera's test not used to detect beta hydroxy butryic acid?

Oh, dude, Rothera's test isn't used for beta hydroxybutyric acid because it's specific for detecting acetone, not beta hydroxybutyric acid. It's like trying to use a metal detector to find your missing keys in the couch cushions - wrong tool for the job, ya know? So, if you're looking for beta hydroxybutyric acid, you gotta use a different test, like the nitroprusside test.