Mini tablets exploded at a time when 3.5-inch iPhones and 9.7-inch iPads were what’s most popular. There was a big gap between these two sizes: the iPhone was highly portable, but the screen meant bite-sized consumption; iPads were better for Internet browsing and games, but it was too large to easily carry around. Mini tablets fulfilled a market gap — a computing device small enough to hold with one hand that offered a better reading experience than phones could provide.
However, the world today is different. The 4-inch iPhone 5S is practically the smallest smartphone on the market, 5-inch phones are average and 5.5-inch phones are not uncommon. The trend to bigger screen sizes is apparent in the chart below: