Dapr's solving distributed systems development at scale. Basically as you grow your team from a handful of people to many separate teams all working on different products, the technical architecture also evolves from monolith to SOA and then microservices. It's the natural logical evolution of anything at scale. Dapr is attempting to provide the primitives you'd need to build any sort of software at scale. Usually this buckets into; authentication/authorization, configuration, data storage, pubsub messaging and a handful of other things.

Full disclosure: I'm the author of Micro (https://github.com/micro/micro) which bakes in the same primitives but also focuses solely on development in the Go language.