Patent search for non-marketed inventions

A patent search can reveal the LACK of activity (blank space) which is useful to identify "Freedom to Operate". The other angle to interpret it is that it is a public source for business intelligence, some inventions are used for internal purposes and may reveal hints about intermediate R&D outputs. There's also specialist search engines which correlate issued patents with employment to identify key personnel which is indicative of market potential as it can take years for (traditional) product development. So necessity depends on whether the cost of negative information is worth it (looking for lack of competition). Note that a lot of IP is in trade secrets so a patent search in isolation may give misleading results.