Here are three reasons why:
• At home, the juice can come into contact with the orange peel, but at Tropicana no juice comes into contact with the peels.
• Oranges bought by consumers are coated with a waxy substance to improve the appearance, which may contain kitniyos, chometz or even casein (a dairy derivative). This is not a real problem year round, but on Pesach we try to be extra careful. (See Kosher Spirit Pesach 5767/2007 and Pesach 5770) Tropicana buys oranges straight from the growers and they are not coated at all.
• All Tropicana kosher for Passover production is done before Pesach so any chashash is botul before Passover. If one juices at home during the holiday with produce that was purchased during Passover, this may not be the case.