This is going to lean heavily on the Sliding Scale of Idealism vs. Cynicism, the Sliding Scale of Silliness vs. Seriousness, and probably a few others lurking in the shadows. There are two undeniable things about the control of fire by human technology and will.
First, it is just about the coolest thing ever. It’s flashy, it’s attention-getting, it’s edgy and dangerous. It is the ultimate special effect. Explosions are good, explosions are impressive – but controlled fire is amazing. Partly because it has the implicit threat of “break the control and Bad Things happen”.
Second, it is one of the most horrific death-dealers known to humankind. To the point flamethrowers as banned weapons of war rank up there with poison gas, and worse than minefields. Burns do massive damage to fragile flesh and bone, healing is long and painful, and if the burns are extensive or in the wrong place, your odds of dying through fluid loss and infection are high, even in a modern hospital.
Realistically speaking, a character that can control fire would be considered armed, dangerous, and possibly too lethal to let walk around unsupervised. You can get a license for a gun. Getting one to use pyrotechnics is much, much harder.
This does not stop fire from being a useful and effective power in realms of magic and superheroes. But it does mean that if you’re trying for realism, or at least verisimilitude, you need to do serious research on how easy it is to set things on fire, how hard it is to put them out, and what are the likely reactions of the average Joe when he realizes the guy next to him is a walking flamethrower. Generally speaking, it would not be good.
That’s always been one of the things that bothered me about portrayals of the Fantastic Four. The Thing gets a bad reaction from crowds in the street, while the hotheaded Human Torch gets all the positive attention. This only seems like a plausible reaction if you’re talking about people who’ve never dealt with the nitty-gritty dangers of welding, forging, making steel, fighting fires, and so many more dangerous things. People in the blue-collar trades, who work with things that can injure or maim if you get careless, would much rather deal with a strong, rock-hard Ben Grimm than a flaming glory-hound.
So if your character manipulates fire, what are their limits? What do people think those limits are? What measures has society come up with to counter them? Because setting cities ablaze has been a threat as long as cities have existed, and no government is going to stand by without precautions.
Giant snowball spells, anyone?