Species currently and historically included in the genus Parodia are very popular in cultivation. Many of them are easy to grow, have intriguing stems and spines and flower easily with brightly-colored flowers. This in combination with their relatively small size ensure that nearly all cactus growers will have some representative of this group. While advanced hobbyists may grow many of the various species and subspecies.
By default on this site, genera such as Notocactus and Eriocactus are included under Parodia. This follows the treatment publications that are readily available, such as the "New Cactus Lexicon". For some reason, the treatment of this particular genus is a highly emotional issue to many growers. It seems they would rather die than to ever refer to a Notocactus by the name Parodia.