Since cute is generally synonymous with small, a fat surrounding itself with cute items/decorations is hoping you will attribute smallness to it by association. They'd rather you call them "cute" as a somewhat acceptable (and therefore believable) lie. The same phenomenon occurs with cosplayers. Hams will dress up as characters that are fit and attractive, in the hopes that by associating themselves with a character perceived as hot, you will find them hot as well. They treat the packaging as a substitute for product quality.