For starters, lip tars are lippies made by Obsessive Compulsive Cosmetics. Initially, they were made as a hippie kind of product– the colors were mostly the primary colors, and it was up to the customer to mix the colors to get a desired shade.
Initial reactions were good because the products were really pigmented, had good staying power, and they were paraben free and instead had peppermint oil as a preservative.
I think it was a combo of the mainstay customers getting tired of mixing and the demand from mass consumers to have this in more shades that they expanded the collection and made a lot of the lippies in ready made colors already. They still have the primary colors kit (with blue, yellow, red, black and white), but for most consumers, they have come up with kits like these.