Just a conspiracy theory, but using sub domains is a trick by many webmasters to "pollute" the SERP with as many results as possible for their site when their company name is searched for. With the increased popularity of UGC (User Generated Content) such as review websites and forums where disgruntled users post bad reviews, webmasters are rushing to push down those pages in the SERPs by using multiple subdomains usually targeted towards information about the company. Now over the past few months we have seen sitelinks being rolled out across many sites and people were asking how to get them and asking for them, now it is open up for you to view via Google Webmaster Tools. So to me it would now appear that Google now wants you to have sitelinks instead of taking multiple places in the results pages.
My tip is to start getting some excellent press releases about your company
