As it should be.
The USPTO is in no place to evaluate a patent's quality, unless youre a USPTO clerk whos first name starts with Albert and your last name ends in -Stein.
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But in seriousness, novelty is the important factor in a patent, not quality. As utility patents/improvement patents are a thing.
The clerks are expected to do a certain amount of work per week and granting a patent counts as more work than denying a patent.
So; clerk are incentivized to grant a patent as it takes less effort and yields more production units. If a patent is of poor quality and later is invalidated in a lawsuit; the clerk will not lose production units. Therefore; the clerk is incentivized to grant patents as they count as more production units and not penalized for granting a patent they shouldn't've.
https://www.uspto.gov/sites/default/files/Examination%20Time...
In fact, the most production units that can be obtained by a patent examiner for any particular patent is to issue a final rejection, get the patentee to ask for re-examination, reject again, and then have the patentee abandon the patent.
Not just "incentivized to ignore quality", they aren't duty-bound to consider quality at all. The PTO evaluates applications for novelty, not quality.
The three main relevant parts of the US Code are:
35 USC Sec. 101: is it patentable? (i.e., it must be a process, machine, process, or manufactured good. It can't be something like an idea or song)
35 USC Sec. 102: is it novel? (i.e., no one single prior existing item teaches all the limitations of the patent claims)
35 USC Sec. 103: is it non-obvious? (i.e., you can't combine a couple of different patents to arrive at your patent)
There's a few other important sections (like 112 that ensures you're giving enough detail), but none of them look at "quality". In other words, you can patent a worthless invention as long as it passes those wickets.
Edit: Somewhat surprisingly to some, they don't necessarily evaluate infringement either. So you could, in theory, have a novel patent that you can't use to make something because it infringes on an existing patent.