I use it also as a valuable tool to gauge interest of a wider audience towards different watches and brands, the instant feedback gives you very quickly an idea where general interest lies.
Also, there are a lot of people you simply don't reach through a forum, particularly the young ones or those with a wide interst in fine arts. A forum such as PPro is where the indepth discussion takes place, whereas you reach a much larger audience through social media.
Best,
Magnus