These items really come in handy at times, as they allow an easy removal of a poké by the very one it should counter via some surprise element of any kind (Sash, SE Berries) and dismantle the opponent team, opening up some sweep possibilities.
NP Doom, for example, can make use of a Passho Berry to get an extra NP against Milotic and possibly kill it (if it gets one NP on the switch and one when Milotic is in), opening a sweep for pokés like Blaziken, Feraligatr and the list goes on.
It's worth noting that all of that is pretty much situational though, as a Passho is not stopping Hitmontop's Mach Punch from murdering Houndoom, but it's worth a try.
As a side note: don't you mean Impish Hippowdon?