What times you are talking about? Professional creators - like composers, poets, etc. - existed long before Berne Convention. Of course, then conditions were different than they are now - J.S. Bach had to write a new cantata every week as the condition of his employment, and also teach Latin and singing to the young. Of course, what was good enough for J.S. Bach is definitely can not be good enough for a person named something like "Jay-Z" or "50 Cent", as the latters' art is much more valuable for the society than Bach's.
As for serving Powers That Be - most of the creative people do it right now, only Powers changed. Some time ago, most disposable income was in the hands of aristocracy and later rich merchants. So they were served. Now due to huge technological advances pretty much everybody has disposable income - so artists cater to everybody. Some of them still cater only to the richest, of course - everybody has his niche. But except for the distribution of the disposable income, not much changed.
As for serving Powers That Be - most of the creative people do it right now, only Powers changed. Some time ago, most disposable income was in the hands of aristocracy and later rich merchants. So they were served. Now due to huge technological advances pretty much everybody has disposable income - so artists cater to everybody. Some of them still cater only to the richest, of course - everybody has his niche. But except for the distribution of the disposable income, not much changed.