I think it is because of the build quality, it is a great device but not built to last, the small size, crappy non repairable buttons and plastic construction are not really suitable for a musical instrument, which typically people would want to use for years, especially given the price and what else can be bought for the same money.
I hardly use mine because of the flimsy build, a real shame because it has some nice sequencing features, if a bit tedious and fiddly due to the buttons.