What about using the USD? And using insurance/lending/prediction markets that use the USD?
USD is not the ideal currency in terms of value stability. I know nothing about Dai, but if it works, its technology could be expanded to other, more material, more reliable assets than USD, and that would be great.
People are working on Dapps for insurance, lending, prediction markets. It is not practical to take out a loan that is denominated in a volatile currency. Also, If you want to bet on the next president in 2020 for example, it is not practical to make the bet using a volatile currency such as Bitcoin.