Hi Jerry,
I think I can perhaps shed some light on this topic and the question posed.
Assuming that someone is aware of the fact that a 22" dish with a sock can produce very nice soft light and a round catch light (if that's desired. some opt for a square catch light. I do at times.) and they're only looking at it from that standpoint then there is no reason to go with the softbox over the dish.
Depending on who you ask, the answer will vary. It can be related to price, size, weight, bulk and location and knowledge.
Like many things, some people will always make decisions based on price and if price is all they are looking at then the cost of a cheap ebay 24" softbox with bracket is almost always cheaper than an equivalently sized beauty dish. If the person is thinking that they may also want a grid then that can add to the cost. This is not always the case and with more and more items like this being imported from China, the cost differential is shifting.
Some people look at size/weight/bulk and like the fact that a collapsible softbox with the bracket will fit into a small bag or a compartment of their lighting kit bag and weighs very little compared to beauty dish. There are lighter dishes and now we're seeing dishes made of plastics so then the reason will turn to bulk. A 22" dish is 22" wide and about 10" deep and that can't change but a 24" softbox will collapse down to an 8" circle. The grid for a beauty dish is also not collapsible and the fabric grid for a softbox is collapsible.
Shooting location can also play a role. If you're working in a studio or your home then the dish makes perfect sense. If you're trekking into the woods then the softbox sounds more appealing because of the packed size and bulk. Many people also work without an assistant, as I do, and there are times when I want to keep things as compact and portable as possible. With a softbox I can have my entire kit in 2 shoulder bags with the exception of a light stand. If I take the dish I still need those 2 shoulder bags but now have an additional item to carry. That's not always convenient.
There are times that I've had to shoot at a location where I have to be as inconspicuous as possible and can't be seen with what appears to be a truckload of gear and again, those 2 shoulder bags lets me move quickly and go wherever I want without drawing attention to myself.
Lastly, there are photographers that are getting started with lighting and don't really understand concepts like quality of light or how we can manipulate, soften and control light. They hear the words beauty dish thrown around a lot but don't always think it's something they should have and are under the impression that the dish and a softbox are so completely different that they choose the softbox because the misconception is that the softbox produces soft(er) light and they like the way soft like looks, not realizing that they can also get very soft light from a dish with a diffusion sock or two.
Those are my observations and conclusions. 
