I think partly this is because flattening the hair at home is difficult and you don’t get great results. I actually put some effort into my natural hair (gel, scrunch, diffuse dry) to get it to look good curly, and the only other way it looks really good is professional blowout to bouncy straight not swingy straight.

Or maybe it’s because wavy hair rocks! I do think curly and wavy, kinky, any hair with texture is livelier than the smooth and straight hair. Like, curly hair is individual and straight hair is standardized.