Not that logic applies here . . . but there's not much logic behind a 24. The standard load is lighter than the 28's 3/4 oz, and you can get 7/8 or 1 oz loads for the 28 as well. (The 24's 2 1/2" chamber is the limiting factor.) Reloading for the 28 is way easier and cheaper, due to availability of new shells, components, etc.
That being said, I had one once: Beretta OU. Nice gun, but choked very tightly, and I wanted to use it for skeet as well as grouse and woodcock. Not many guys out there with the tools to open 24ga chokes, especially on chrome-lined bores. Caused me to let it go fairly quickly. I did discover, quite by accident, that it would fire 28ga shells, although they'd slip past the ejectors.
