Still.. I've got no clue why someone would be interested in watching anyone stream instead of just playing yourself.
Personality of the streamer.
Watching a game you don't have access to, such as beta, or just a new release you're not sure on buying.
Streamer's more skilled than you, so you're learning things that skilled players do.
Anyway, I actually prefer watching healing. If I watch a Fatboss guide, and it's done from the healers PoV, a lot of the time I'll end up zoning out of what they're saying and just watching the raid frame.