Would you, if you could better handle those checks/counters with other members of your team first?
That's what I'm getting at.
That's the point. You don't. You don't because the moment you get rid of said check/counter with a mon (specifically, a setup mon op af as most of them are) that isn't suposed to do so, you have already won. This is not like Hidden Power or having niche and less frecuent coverage moves that lets you put a hole in the opposing team using diverse type of mons; this is a mon that is already difficult to stop if it wasn't for a few checks it has ending that situation and running through them.
I'm not saying that you couldn't use tera in other ways, oc you can, and I'm not even saying that you shouldn't. I'm just stating that a majority of the teams, depending on how weak they are to certain threats, have 1/2 checks/pseudochecks to certain mons that, I repeat, are already difficult to stop and the only reason you are able to do so is because you have a type and knowledge advantage -you how what they do in order to win-. My question, again, is very simple, what will your team do when said mon, or mons, get obliterated or setup in the face by a mon that you are suposed to check but, unlike with hidden power or a random niche move that you can scout, now it is the one checking you.
What does your Heatran mean to a random teratype volc? Nothing. And tox? nothing. The rest of your mons arent even able to answer it after a QD, and now it has a new stab you dont have answer to in your back, because you dont even knew what that type was during the battle, so you didnt come to say "i better save this mon for later" at any point. And this is not a suposed Volc setting QD turn 1 and fighting a 1v6 at 100% health. No, this is a real scenario in which 2-3 of your mons are already dead and you think it cant setup because you still have that one counter that, oh, surprise, wasn't even a counter from the very beginning.
I think it doesn't necessarily have a wrong answer, since you'll be thinking about the meta you're playing in and very specific threats you might face. But if there is another Pokemon available that can handle those threats, I'd expect someone to go with super-STAB most of the time.
Which makes it even more dangerous.