Decoration exists for comfort, beauty, and usability. I particularly like this fantastic essay that explains the rationale for decoration in architecture, and how the current design preferences for stark simplicity came to be.
https://www.currentaffairs.org/2017/10/why-you-hate-contempo...
An excerpt: 'A few obvious stylistic changes characterize postwar architecture. For one, what is (now somewhat derisively) called “ornament” disappeared. At the dawn of the 20th century, American architect Louis Sullivan proclaimed the famous maxim that “form follows function.” Even though Sullivan’s own buildings were often highly ornate, adorned with elaborate Art Nouveau ironwork and Celtic-inspired masonry, “form follows function” was instantly misinterpreted as a call for stark utilitarian simplicity. A few years later, architect and theorist Adolph Loos, in a 1908 essay called “Ornament and Crime,” dramatically declared that a lack of ornamentation was a “sign of spiritual strength.” These two ideas quickly became dogmas of the architectural profession. A generation of architects with both socialistic and fascistic political leanings saw ornament as a sign of bourgeois decadence and cultural indulgence, and began discarding every design element that could be considered “mere decoration.”'
