Why have to join ten communities and have to know all their ins and outs when you can join one (and still join the others if you want to)? That's rhetorical (but I'll try not to be offended if someone answers it). It sounds like a major headache to me (and reminds me of a university class where there are five distinct physical, digital and lecture sources to glean all your different homework assignments and due dates for one class, and three buildings to meet at different times for different activities where you have to cross reference different books in real-time to get the information to answer questions posed). That's not fun for someone like me, but some people seem to love it—I don't quite understand, but I'm guessing they must have more of the right kind of working memory or something (and a lot more time to waste, unless they think it'll save people more time outside of school or something, and train them to be extra-qualified corporate executives or such). Truly, what you suggest isn't nearly that bad, but I think Software Recommendations has a definite place.
Also, some people are specifically interested in software for the sake of it being software, and have been since they were maybe four (e.g. me; I'm nearing 40).
I don't tend to browse questions here often without looking for a specific kind (at this time), but the site is still a great relief to me. I like to look for a wide variety of different kinds of software, for different purposes (in different areas of interest; e.g. music engraving/listening/playing/etc., games, gardening, database, enhancing computer use, programming, software that assists in making creative works, cryptography, accessibility, language-learning, learning, operating systems, etc.)
One thing you're perhaps not as likely to find on a number of the specialized sites is people who are knowledgeable about free-software, open-source software, software licenses (and their consequences), Linux software, etc. It's more likely on those sites than on this site (IMO) that you'll get recommended Windows/Mac-based freeware, adware, or bloatware (or else something that costs a lot, and is still for Windows/Mac only, or else they might recommend some website when you want something that isn't web-based). If the people are experts in their field, that doesn't necessarily mean they're experts in the software available for their field (although they're sure to know what's widely considered popular and good, which in some cases is open-source, free-software for Linux). However, a lot of people in other sites were members of Stackoverflow first—so, any StackExchange site is likely to have some members with some level of expertise in these areas of interest.
There definitely are people who really know their software in various specific fields. However, that doesn't mean they know the kind of software you're looking for. Software recommendations is definitely it's own field of study, IMO. If large businesses knew what was best for them, they would desire Universities to offer a degree in it. I mean, we could put Gardening and Landscaping, Seasoned Advice, Botany, Biology and Health all in the same site if we wanted to, as they are pretty interconnected, but they exist for a reason.
I think enlarging other sites' scopes to include software recommendations should be up to the sites themselves. Some sites will probably want it, and some won't. However, even if they all wanted it, I don't think it would replace Software Recommendations much more than if we dissolved Stackoverflow and allowed on-topic programming questions on all the other sites. Obviously, programmers probably aren't going to be congregating in large numbers on some of the other SE sites, even if there could be all kinds of programming questions relating to a particular site. In the same vein, you're going to get different answers here than you will on other sites, and you may not always prefer one site over the other for the purpose.
People here are also more likely to understand software terminology than on the non-technical sites. So, when you list the features you want, they may more readily understand what you want (and they may even have more insight into why you could want those features).
Another issue is that some SE sites are new, and new ones are always coming. A site with a steady user-base is going to be more reliable for software recommendation questions. Smaller sites may not get many answers to such questions for that reason.
An idea that I personally like more is to have users be directed here from all the other sites. Let this site have a tag for each community, and let all the other sites direct their users to that specific tag on this site (in their own help center or such).