Answer: to minimize exposure and/or seek a windfall. Non-publication keeps others from knowing what you are up to in your patent filings. This offers a cloak to inventors or companies preferring discretion.

Submarine patent launches may be particularly advantageous to patent players seeking a competitive edge, especially in an area subject to rapid innovation, as evidenced by a contemporaneous patent filing flurry.

35 U.S.C. §122 (b)(1)(A) Subject to paragraph (2), each application for a patent shall be published, in accordance with procedures determined by the Director, promptly after the expiration of a period of 18 months from the earliest filing date for which a benefit is sought under this title. At the request of the applicant, an application may be published earlier than the end of such 18-month period.

35 U.S.C. §122 (b)(2)(b)(i) If an applicant makes a request upon filing, certifying that the invention disclosed in the application has not and will not be the subject of an application filed in another country, or under a multilateral international agreement, that requires publication of applications 18 months after filing, the application shall not be published as provided in paragraph (1).

A non-publication request must be rescinded by notification to the patent office if an applicant subsequently decides to file internationally, or the application will be considered abandoned; refer to 35 U.S.C. §122 (b)(2)(b)(iii, iv).

Given the default to publication, with relatively few taking the non-publication route, it becomes possible to spot patenting flurries, though, of course, not at the leading edge. Nonetheless, even a two-year lag provides a window that allows a savvy inventor to catch the trend, and leap ahead with unanticipated extensions in the same technology, snagging small claims within the gold rush patent territory.

The offensive impact potential of a submarine launch may be considerable, depending, of course, on the inherent value of the claimed technology. Companies invest in a technology, seeing freedom to operate (not knowing of the submarine). It may even be that a company files a patent on the same technology as the submarine, though subsequent to the submarine. When an unpublished submarine is allowed, the cost of substitution (non-infringement) has been raised, owing to customer expectations having been set towards the infringing feature(s). In such circumstance, patent licensing may be a net less-cost alternative to substitution; the submarine shines gold.