People are different, each one has his / her own preferences, views, interests. Sometimes what is boring or difficult for one can be interesting for another. Where one person sees difficulty, another person sees a challenge and a chance. The world is colorful and that's fine.
Many reasons can be ascribed for this. It is quite possible that a particular faculty is working on a topic which is of more interest at present. As long as you are contributing to the body of knowledge it is a good topic for indepth study.
When studying for my Masters many years back I put in research topic, The Consequences of Money on Athenian Society. Yes, it was rejected and I was told my premiss was wrong. I refused not to do it. I found subsequently only 3 other people tackling the subject.
My supervisor knew nothing of the subject. Didn't wish to admit it. Instead of placing me elsewhere (honestly I don't think any of the Professors then understood it in its entirety) she refused it. As above, I continued despite that.