The most obvious and important one is a negative consequence: creative self-indulgence. Nikki Hilton designs expensive handbags (which is still, admittedly, a more admirable way of spending a life than the one her sister models). There is a reason most product and service ideas in the world are created for and by rich or middle-class people for their own classes. The turpentine effect is far more prevalent than its utility requires. There is a limit to how many people can be absorbed in safe and socially-useful turpentine-effect activities like tool-building or teaching. Let loose where a content-focus, artistic eyes and judgment are needed, it leads to over-engineered monstrosities, products nobody wants or needs, and a massive waste of resources. Focusing on the problems of others, rather than your own (or of your own class), requires even more effort.
The positive effects are harder to see, but they are important. The turpentine effect is how isolated creatives can get together and form creative communities that help refine and evolve a discipline, sometimes over centuries, and take it much further than any individual can. Socially, this emerges as the aesthetic of classicism in any field of craft.