theres really only about ONE reason to use the crappy trainer

Lets say you're playing a deck in which they have a pokemon you have resistance to. I.E. Scyther and Hitmo's, well you can let them have a extra pokemon on the bench, but remember, keep those hitmo's active so you can pound on them for free, OR use your resistance to stall while you charge up the calvary. Thats it, just fill their bench with the stuff that can't hit you. But you know, you'd need quite a lot of pokeflutes, so its best used against one color decks where you have a pokemon resistant to that one color.