If you're checking its listing on Pokemon in singles formats, a lot of Pokemon that get Pollen Puff also get Bug Buzz, which is better because of the Special Defense drops and ability to pass through Substitute. Pollen Puff does see niche use on Pokemon like Calyrex-Shadow, but most of the time a Pokemon has better options.
Checking Doubles formats changes the listing a bit. As Pollen Puff's bonus of healing allies can actually be used in these formats, it's not considered a "usually useless move" as often.
Source: Checking Showdown, experience, and this