That changed in the last 15 years and now it is strongly recommended by most practitioners that the words "prior art" do not appear in a patent application and there is not a listing or discussion of previous work.
The reason for the change is that people were accused in court of misleading the examiner, for example, by saying - Patent X doesn't teach method Y when you haven't studied patent X thoroughly to really know that is true. We do need to let the patent office know about anything we know. That is done just by listing items on an Information Disclosure Statement form. There is a place on the form to indicate page numbers or sections of each listed prior art. Most practitioners do not fill that in for fear of being accused of hiding the ball if a court finds that a different section was more relevant than the one you specifically pointed out.
There is always prior art - but it is not always dead-on. Yes, it is the examiner's job do a search and see how the claims are anticipated or shown to be obvious in light of the prior art.