Imagine that you have an uncle that lives in Australia that you visited as a little kid. And you got your ass kicked by a kangaroo. You very reasonably might become afraid of kangaroos.
But years later when you go back, this gets in the way. Your uncle now has a pet kangaroo, and it's a total sweetheart. But you're stuck with this fear. So you determine to get over it. You spend more time with the kangaroo. Pushing yourself closer and closer, while paying attention to the fact that it's actually playing nice. Eventually you'll get comfortable with the thing and you're not afraid anymore. Yay systematic desensitization.
And in addition to getting attacked by a kangaroo, you developed another fear. On your first visit, you were just not watching where you were going and you ran into his ham radio antenna. When you looked up, you had no idea what you were looking at. It looked like this giant monster which hurt you. For the rest of the trip, you wouldn't go near the monster. That thing was scary. When you were walking around the neighborhood and saw another one, you screamed and demanded everyone turn around.
But when you go back as an adult, things are different. You don't remember exactly what it was you were afraid of, but you remember it being this big scary monster thing. So your uncle takes you out back to show you. And after the big reveal.... it's just funny. It's just like "I was afraid of that!? Haha, that thing doesn't even move!". You don't need to systematically desensitize yourself. It's just a non issue.
And these two situations are fundamentally different. Even at the neurological level. And they behave differently.
Look at fear recovery. You're petting the kangaroo and you aren't afraid of it anymore and everything is great! Then it bares its teeth at you. What do you do? You flip your shit. Fear is back in full force. However, what happens when you bump into the antenna again? Does that fear come back too? No. It's still an antenna. Big difference.
In the kangaroo case, what you learned when becoming unafraid is that the base rate of kangaroo attacks is lower than you thought. That's the reason you don't want to go right up to it - it doesn't feel safe yet, and you have to accumulate statistical trials before you're willing to drop your guard. But you still know that kangaroos can kick your ass, and that it does happen. So of course when it shows signs of aggression, it brings the fear right back. Not only is that one trial a huge update on your base rate estimate, that estimate don't mean shit when you have an aggressive kangaroo in front of you.
And this is what we find when we shock lab rats and do extinction trials. It really looks like we're just learning an inhibition to patch over our still-existing fear response.
But in the antenna case, you're not accumulating statistical data. You just learn in one fell swoop that it's an antenna - not a monster. You're still afraid of monsters, of course. It's just that no amount of bumping into an antenna makes it a monster. You didn't tentatively learn "safe for now", you learned "I was fundamentally wrong to have been afraid in the first place".
And that is the difference between extinction and reconsolidation.
Reconsolidation just sounds way nicer. You get to laugh, and relax. Instantly. Fears don't come back. All good shit. It makes no damn sense to slowly extinct your phobia of butterflies through systematic desensitization. I mean, it'll work, sure. It's way better than nothing, sure. If that's what you know how to do, do it. But like... it's clearly not the right solution. Butterflies never should have been scary in the first place. If you're looking for how to solve butterfly phobias right, look for reconsolidation.
However, extinction has its place. Sure, maybe you could reconsolidate to some extent by learning to put your uncle's nice pet in a different implicit reference class than wild kangaroos, taking into account other factors, etc. However, whenever there's something that really has given you reason to fear it and you can't find a remapping that shows the reasons to be mistaken, it makes sense to keep that fear response inhibited and ready to spring back. If it's not there, then you won't react in time when the kangaroo sits back on its tail preparing to double kick your ass.