Models with constant-volatility random walks aren't favoured over "fractal" models because of some elaborate charade or flawed incentives. They are used because they are tractable models that can be used to make predictions. Fractal models are not.
Financial models are just like any other engineering tools. They approximate reality so they can be useful; but violate their assumptions or use them outside of their intended purpose, and they're likely to blow up in your face.
Financial models are just like any other engineering tools. They approximate reality so they can be useful; but violate their assumptions or use them outside of their intended purpose, and they're likely to blow up in your face.