Do PhD students really publish so committee doesn't have to thoroughly read dissertation?
Some thoughts on this:


It certainly helps the committee if (parts of) the thesis were
already assessed before - along the lines of "If somebody else already said that
this is good then it can't be that bad after all".
It also helps the student to convince the committee that this is
mature enough for graduation (same argument as above).
Some universities allow cumulative theses i.e. introduction + 3*
pdfs of first authorship papers + discussion. (* the number depends
on the field). This is mainly as writing a thesis with several hundred pages is something you will never need again even if you continue in science. Most fields just publish in short journal article nowadays and writing 200 pages about a content that can be covered in 5 pages is not a skill you need (and nobody wants to read these 200 pages (including your committee)) - sounds mean but it is like this.