The large use of very pure water and potting mixes which contain a significant amount of inorganic substrate and little in the way of decomposing organic matter. Leads me to my own personal theory that in cultivation the plants are getting less nutrients than they would in nature via the soil. This makes it even more important to suppliment through feeding. Preferably in some sort of 'natural' fashion with insects and whatnot instead of inorganic fertilizers whenever possible. Remember carnivorous plants grow in nutrient poor environments not nutrient devoid. These environments are capable of growing even noncarnivorous plants reasonably well but the combination of supplimental nutrients via trapping insects gives carnivorous plants an edge to out compete the noncps to some degree.