My view on a dissertation -- whether it be for a masters degree or a Ph.D. -- is that the contribution is not the important part. Instead, the goal is to demons

My view on a dissertation -- whether it be for a masters degree or a Ph.D. -- is that the contribution is not the important part. Instead, the goal is to demonstrate an ability to do "good research" (TM). People find very narrow topics because thesis advisors prefer it. If you had an already well-studied topic, it is more difficult to access as original work. Yes, ideally you want to find something novel, narrow, and practically useful, but grad students primarily want their degree first.