In certain situations it may be undesirable for the outside world to know that the user owns some music file.
For instance, some songs are political, and repressive governments might monitor the citizens' Internet traffic for traces of forbidden song titles.
If qmmp plays back such a song and tries to fetch the lyrics automatically, the government might be able to observe the metadata request to the lyrics server, and deduce from this that the owner of the IP address owns the forbidden title, leading to incarceration or worse of that qmmp user.
It would therefor be nice if the lyrics fetching module became a button for explicitly fetching the lyrics for the currently played-back song.
Of course, if the lyrics are already in the cache, they can be displayed anyway, because no network access is required.
I also recognize that not all users live in countries under repressive regimes and might not not need this feature. Automatic or manual lyrics fetching should therefore be an option setting.