Any time you see an article or news report about something that involves an assload of energy, it's always the Hiroshima bomb they compare it to. For starters, it's absurd since it happened over 65 years ago, and most people alive today weren't even born then. Furthermore, if you asked random people just how much energy the Hiroshima bomb involved, they wouldn't have a clue. Same with the blast radius, the cloud peak, and even the number of people and buildings destroyed. Nobody really knows, so it makes for a shitty comparison object.
Secondly, most of the time the comparisons are like "It released a hundred and fifty thousand times that of the Hiroshima bomb!"
The point of a comparison is so you can easily identify in your mind the object or event in question. If you have to envision a hundred and fifty thousand of them, it doesn't work. That's like explaining to someone that the Colosseum has so much interior space that it could accommodate thirty million ping pong balls. It just doesn't work.
Besides, they say it as if the Hiroshima bomb was actually large in terms of nuclear detonations. It was a firecracker compared to some.