The OSM is really important project. Like Wikipedia or GNU in the older days, maybe even more. And like everything open-source, community-driven, it's strongly dependent on how many people use it. Because, obviously, you are more likely to be wishing to contribute if you are using it yourself and, preferably, depend on your friends using it. And OSM is the kind of project that pretty much everyone potentially could contribute to, because local knowledge is invaluable for that kind of stuff. So caring for usability for everyone should be the primary goal, I'd assume.
Yet OSM is kinda "b2b" in terms it's important for stuff like Foursquare running, but is close to unusable for the common user without stuff like MapBox, Foursquare and such. Because, really, what "common user" cares for? Where to find café nearby, how far is it from point A to point B (usually in some comparatively small area) and only very little information about the whole world (like major cities, country borders). More importantly, whatever information is there, he want's it to be usable and accessible. That is, being fast to navigate, ability to make marks on your local device, accessible in offline. Ideally, of course, you'd also want to have seamless integration between offline and online modes, ability to share your local maps, there's always something more to wish. So I feel that existence of good clients for all platforms and ability to extract information you need for them easily (without any self-education for that purpose at all, really) are absolutely must-have.
Well, alright, we cannot expect somebody else working for free to provide every single service we want after all. If you want something done, do it yourself, right? It's how the open-source works, really. And that's the real problem: documentation is horrible, both for "common users" and "power users" (potential developers). There's quite impressive in sense of size wiki, but it's totally awful in sense of usefulness. It's very hard to get going if you are completely new to project and don't know anything about cartography. There's basically only one thing I want to know when I find anything new: how to use that thing. That is "Getting started" guide, followed by links to "What's next?". OSM wiki has something called "Beginners' guide", but it must be a joke, as the only thing it does is explaining how do I actually edit that map, and that isn't really "using". (Again, if we don't think of it as b2b only, which I explained why I think it's wrong.)
The same time there're articles on very wide range of topics, like existing software clients or "Why open data is important". But you aren't guided to stuff like that. And they are even worse. For example, why'd you care for existing clients? Right, you want to find one for your device. There might be several bests, sure, but neutral-point-of-view-style listing of a hundred of them does only a little better than nothing at all. If you want to know what you have to do (or know) in order to implement your own one — it's even worse. The typical github project probably has better API overview than OSM (and usually even includes some domain-specific knowledge you probably don't have if you are new to the field, which is absolutely natural in case of cartography).
If you want to see an example of good thematic wiki, look at ArchLinux wiki.
Overall I think OpenStreetMap is better of having small projects like WheelMap, OpenFireMap, SeaMap, CoinMap etc. because there is less or even no competition at all. Many of these things can simply not be done the same way with google.
What you are suggesting is competing with google maps with basic services, where OpenSreetMap is worse of at best sometimes equal. Why should someone use OSM to get from A to B when google and every navigation system already do that perfectly?
OSM is not both. It is a project for editing and creating a free map database over the world. The site, the community and the wiki is all geared towards attracting editors and making the data they contribute as high quality as possible.
It would be good if we had a project to make it easy to use and develop application on top of the free data OSM provides. Its not OSM goal for now, so the spot is open for anyone who feel they can make a difference.
But I can't for the several reasons. First off, I don't have enough domain knowledge myself yet to improve the docs or even confidently develop for OSM. And, yes, I'm planning to correct this omission, but not even soon enough.
The second reason is, that b2b model I pointed out to be wrong in my opinion is the very idea of OSM at this point. You can see claims quite often, that stuff I mentioned isn't important, because OSM is the data, not the service. That's why I've written this post, explaining why I think ignoring "the service" part is hurting "the data" part, in hope that somebody from OSM community would read it.
On the "b2b" thing: I think that's a mischaracterisation. It's not "to business" specifically, it's to anyone who wants to make use of the data. There are already OSM-powered consumer-grade mapping sites for particular verticals (I run one for UK cyclists, http://cycle.travel/map) and more are on the way.
But it's not true that osm.org goes out of its way to avoid being a consumer service. It may not be the prime focus (and nor should it be) but there's a lot happening on the user-facing side of OSM: a significant redesign last year, lots of stylesheet improvements underway, and routing going live in the next couple of months, for example.