It's somewhat of a false myth. First, as the article notes, the reason was related to coal transport in mines, not wagon wheel width. Second, different mines

It's somewhat of a false myth. First, as the article notes, the reason was related to coal transport in mines, not wagon wheel width. Second, different mines in the world use different widths, many mines being narrower. Third, the victory of this gauge was incidental. Had Brunel picked a broader, but not so huge gauge - like many people did across the world - perhaps the result would have been different. Lastly, the actual standard gauge is a bit broader than what Stephenson had in mind in the beginning. Though he may have agreed to it. I dimly recall a quote by him that if he had done it again he would have taken a few more inches but not many.