Or not. One could also think that knowledge, of whatever subject, no matter how small and unimportant, is a good in itself, which does not need a further purpose.
As far as I am concerned, I always look for a purpose's purpose. Things become significant for me only insofar as they are part of a larger frame. I am happy to focus on the paper of a manuscript I am working on, I find the evolution in a letter's shape fascinating, I spent months on rare terms, such as prasaṅga. But I would not be able to do it, unless I thought of it as a step towards a better picture of, e.g., the development of Indian thought. Apart from my personal tendencies, I believe that focusing on the significance of what we study is ethically right. Also because human resources are limited, and I do not think it does not make any difference whether they are employed in trying to understand a miliar stone of Indian philosophy, or on a minor line in a minor work.