The key point is as described - to secure a patent you have to declare what you have done, and hence make it public. Of course, a clever team could file patents that are completely useless or red herrings, but that's all work and income for the lawyers, and all with no real value to the team - by the time the patent is approved the regulations will have moved on. As has also been mentioned, the ruling bodies don't like teams to have unique access to an advantage - and the rules will change to prevent use. Google Kinetic technology in WRC or Dakar as an example. This has a disappointing side effect - the teams aren't inclined to invest in externally sourced patented technology developments - as there's the risk that if it works it will just get outlawed and all the investment is wasted. Lastly, there's the issue of enforcement. How can you identify and proove patent infringement without access to the cars ? More work for the lawyers...
"I am not designed to come second or third. I am designed to win" - Ayrton
The J damper was based on published academic papers. I can't remember if it was also patented. So using published research can be used without the other teams realising, although I expect that's the exception.
