Large network buffers can be thought of as 'dark buffers', analogous to 'dark matter' in the universe. They are undetectable under most circumstances, and you can detect them only by indirect means. Buffers do not cause problems when they are empty. But when they fill they introduce additional latency (and create other problems, possibly very severe) to other traffic sharing the link.
The Buffer Bloat project is dedicated to finding and mitigating Dark Buffers.