The seasons are: (1) as Ecchu fundoshi has the ultimate shape in its kind, the design has not changed for a long time, manufacturers can only make a difference in material, color or pattern; (2) as the most typical color for the fundoshi is white, there is extremely limited demand for other colors or patterns, and thus making a difference cannot be paid off; (3) since this is not so difficult to make, as they were made at home in the previous period, the price and profit rate should be low accordingly; and (4) it's hard to expect a large sale that can pay off the capital investment, as it's hard to expect a growing demand in comparison to other undergarments.
越中褌が究極の形状であることから、昔からデザインの変化がないことで、材質や色か柄でしか商品として差別化ができないこと、白色が定番の越中褌では色物や柄物では極端に需要が少なく採算に合わないこと、個人でも縫製できるものであるため、単価も安く利益率が低いこと、他の下着と比べて需要の伸びが大きく見込めず、設備投資に見合う大量販売が見込めないことなどである。