As someone with a postgraduate background in Philosophy I can say that, within at least the Western Analytic (mostly anglophone) tradition, that many do in fact think exactly that and I would tend to agree. Many Philosopher see their closest relations reside in Mathematics and to a lesser extent the hard sciences. They prize deductive reasoning and argument with truth as the aim.
They are not consciously engaged in a project of cultural preservation and would welcome say Indian or Chinese contributions, but the barrier to understanding their contributions are often very very high (conceptual and not just large linguistic barriers with lack of access to good translations) and so very few people bother to engage when grant applications need writing.
History of Philosophy, as the study of past traditions, thinkers, and arguments plays an outsized role in Philosophy 101 undergraduate courses, but in fact represents a minority of research activity. The majority of research philosophers are active in work relating to new work and living or recent figures such as David Chalmers, Saul Kripke, Ted Sider, David Lewis, Ruth Millikan, Dorothy Edgington, Timothy Williamson, David Parfit, and many many others. To demonstrate what I mean look at the citation network of the top journals in the subject:
Force graph visualisation: https://kieranhealy.org/philcites/
Blog post explainer: https://kieranhealy.org/blog/archives/2013/06/18/a-co-citati...