Take the german 10J-Bundesanleihe for example, as far as I know the rates for it went negative recently.
Is there any incentive for private investors / or institutional ones to invest now into this product? Because just keeping your money with yourself, has for my limited knowledge, a better "ROI" then buying it now? Or is it because you are free to trade it, a speculation on the future that the "ROI" indeed will rise (and so the value with it)?