Is art a luxury, or is it something we do?

Talent for creating works of art would never have evolved if art was not necessary. 

IMHO art is something we all do and cannot help doing.

Planting bulbs in a flowerbed, finding the right accessories for the dress and for the occasion, decorating the cake, ... we do art in hundreds of ways.

It is an expression or message.  Not a luxury at all. 

Owning some of it is a luxury. 

A necessity.

Without the arts in their broadest sense, except perhaps in a very restricted, purely-functional way, society would be very much the poorer for it.

Mankind world-wide throughout known human-historical time has always needed to express itself artistically, for many reasons. Just a couple of examples:

Some of the prehistoric cave-paintings of Southern Europe are extraordinarily vibrant, beautiful illustrations of animals, drawn with great skill with charcoal and ochre on deeply-undulating rock surfaces. They may have had ceremonial significance but we have no way of knowing this. Bronze-age artisans loved to ornament purely functional tools like earthenware cooking-pots or bronze mirrors, with designs that would grace modern versions.