Normally, lyric sync is a natural thing to do, but doing it just for the sake of doing it (and moreover, doing literal lyric sync) can mean the video just gets confusing. For a comedy video, this isn't a big deal or may be exactly how it should be done, since comedy videos tend to rely very heavily on the lyrics of the song. For a drama video, though, you'd probably need to get creative to make sure you can carry the video's plot while still making sure the lyrics make sense to what you're showing (or don't appear stilted). So with those it's more about give and take.
The tl;dr version: lyric sync is an art and takes an understanding of nuance and of what kind of video you're making.