HTML is presentational in nature, so what's the point of separating presentational attributes from presentational tags? With the current spontaneously emerged

HTML is presentational in nature, so what's the point of separating presentational attributes from presentational tags? With the current spontaneously emerged HTML standard we have a choice of using or not using separate style declarations, like in imperative programming we may decide to declare and give a name to frequently used constants, macros and functions separately. A library, in other words. Is library obligatory in programming? No. That would be just ridiculous.