Patents can be very valuable assets to start-ups and those with new inventions. Procuring a patent, like any other worthwhile business endeavor, takes a lot of time, effort and money. Because there are so many resources that go into obtaining a patent, seeking patent protection without first performing prior art search is extremely inadvisable.
Consider, why would an inventor or a business invest so many resources into filing for a patent without a reasonable assurance that the invention is new? In addition to protecting against wasted resources, a thorough search may reinforce the strength of any patent that might eventually issue. Patents that have not been thoroughly searched may get invalidated if prior art later shows up that teaches the new invention. While the patent office performs a search in the process of examining a patent application, the patent office has limited resources and thus may not conduct a very extensive search.