I think the point is that structure and style should be decoupled, i.e. the way something looks (color, fonts, borders, etc.) should be defined separately from the way something is shaped.
I entirely agree they should be decoupled; so why are they being combined by having you write what's essentially inline CSS in your HTML? I thought the point of CSS was to do away with that, because of how inflexible it was, and to move to a more declarative setup.