Most responses tell you to add them yourself which is a solution to this problem. But I think the reason why the state of businesses on OSM and Organic Maps (which uses OSM as a source) is so dire is interesting too:

OSM must not use other maps as sources. In fact, they must not use any information that hasn’t been licensed in a way that specifically allows OSM to use it. As such, they can’t just go to Google Maps and copy all the business information over because Google has not licensed that information in an open way. Information like streets, paths or houses can be gleaned from satellite pictures that have been provided to OSM and can be put in easily so they tend to be up-to-date. But for businesses, someone has to actually go there and confirm the information.

Now why is Google so good at that? Because almost every business owner makes sure to put their business on GMaps themselves and keep that information updated so it doesn’t depend on one person going through the area regularly.