That doesn't support your argument at all suggesting a Life Orb would be better. And how else do you expect to play a bulky menace like Volcanion without slow U-Turns or switching into obvious Fire, Water, Ice and Steel moves? Of course you don't switch Volcanion into Garchomp or Tyranitar, but you don't switch Heatran into those either, nor would you give Heatran a Life Orb. O_o This plead to prediction is a universal component for any pokemons success, but the point is the combination of Specs STAB Overheat and Steam Eruption being so naturally powerful and difficult to switch into that the risk/reward ratio of such a set is greatly in Volcanion's favor. Ironically other Volcanion are pretty much the safest switch and even they fear Stone Edge/Earthquake. So I don't understand the consistency in your arguments. And I'd hardly say Volcanion and Heatran are interchangeable. Many of their weaknesses are different and Volcanion has a much stronger spammable move.