A question about Art

I was once told "commissioned art is always bad art." Granted, any saying which contains "always" is a prime suspect for exceptions (notice how I avoided always there. . .) but this seems to me a particularly objectionable example. In sculpture, can you name any great works that aren't commissions? Phidias, Michelangelo, Donatello; their whole careers are based upon commission work. Really, most any physical art (in other words, leaving out literature & music composition, the starting line was directly in reference to visual art so I don't feel bad leaving them out) dating from before the nineteenth century is a commission. Prior to that society didn't generate enough surplus wealth to create a speculative art market, and those with enough income to avoid the need to work to live were restricted to the upper classes where being an "artist" as a way to while away the time wasn't socially acceptable. A warrior, a clergyman, a scholar, a poet? Yes. Though most often a combination of several of these. A painter or sculptor? No. For the overwhelming majority of human history, art IS commissioned art. The artist who can create a living simply because he is an "artist" and a ready stream of faux-intellectual nouveau riche twits wish to purchase high culture street cred is a product of the industrial revolution as surley as interchangable parts, trade unions, and smog.