Prediction has multiple layers, Dre. If I think your Tauros is going to EQ my flying-type, predicting a Gar switch, I can leave it in and hit you with an Articuno Blizzard or Gyarados Hydro Pump. And if I think your Rhydon's going to Rock Slide my Gar, predicting a flying-type switch, I can leave that in too and kill you with Mega Drain.
The point isn't having 100% safe switches, that only works against noobs. The point is having the advantage.
I mean, I've made three-layer predictions before (predicting that Tauros will Blizzard predicting my switch to Rhydon predicting a Tauros Hyper Beam, and staying in with Chansey for the Thunder Wave, for instance). There's no limit to how far mindgames can go. The objective of having Gar, and having Flying-types, is to make your opponent play those mindgames instead of being able to mindlessly Body Slam with Tauros or mindlessly Earthquake with Rhydon or mindlessly Thunderbolt with Zapdos or whatever.