Earlier quoted context omitted.
The patent is invalid if prior art exists,so publishing it is enough to avoid it being poached by others
But doesn't the patent office only look at previous patents when searching for prior art? Of course, other sources of prior art can be brought in as a defense, but it still may not stop someone from getting a patent initially and using it to harass financially weak opponents.
Lack of patent examiner familiarity with the industry, history, and the state of the art is traditionally considered a weak point in the system as a whole. Supposedly when writing the patent claims you're supposed to do a search to make sure you're not conflicting with other patents and that there is no prior art, but this is often used to word the patent in such a way to avoid the prior art from invalidating the patent, or use differences with the prior art as support for the uniqueness of the patent being applied for. Unfortunately, patent examiners are traditionally illequipped to accurately make an assessment, and the patent applicant is allowed to make adjustments to address the issues the patent examiner found. I remember there was work on getting patent examiners to be more familiar with the areas the patents they are examining/approving are for (technology, software, or business, for example), but I don't know where that stands today.
However, IANAPL and IANAPE.