Not the above poster but I’ve had dentists share the same sentiment and mostly I’ve heard it’s because the majority of their patients who use it, use it as a replacement for more thorough dental care–they don’t floss and/or brush because they think they’re getting clean enough with the pik. The dentist who told me this basically said, “It’s fine as a supplement after you brush and after you floss, to flush out any lingering debris from those two activities, but it’s really just not worth the time or money.”