Why why we need blockchain technology, in a nutshell

In an ideal world life would be very simple, which includes that we wouldn't need blockchain technology, or indeed there would be very little or no need for technology. But we do not live in an ideal world now, where it is not possible to engage in economic activity and place trust in a trusted third party without the risk of corruption, misuse of power or abuse of trust. So blockchain technology is very important, as it can eliminate the need for a trusted third party while reducing transaction costs for all kinds of economic activity.