For better or for worse, investors are not always able to make their own independent judgments with respect to the quality of an underlying technology that is the basis for a start-up company. What this means is that investors typically look for other ways to gauge whether the underlying technology is sound, including looking to the United States Patent Office for some kind of independent verification from a neutral party regarding the merits of the technology. While the Patent Office cannot and does not vouch for commercial feasibility, when you obtain a patent it should be at least some evidence that the technology or innovation included in the application is unique to some level, at least based on the references that could reasonably be obtained with a competent patent search.
This is one reason we want the Patent Office to do a credible job in examining applications. Another reason is simply to have a database of valuable information, so that anybody (venture capitalist or other) can go to the file of issued patents and have a reasonable expectation of finding things that are useful, novel, and nonobvious. The Lemley approach of "rational ignorance" gives no value to the societal benefit of having a trustworthy repository.