This question has many answers for many different people. For some, decentralization is a goal in and of itself. A sort of return to first principles that made the Internet compelling in the first place.
For others, it has to do with more pragmatic concerns like not interrupting their workflows when one company's systems go down. Others have concerns about how much trust they put in one company to treat them and their data fairly through changes in ownership, business model, etc.
We think these, among others, are all good reasons to prefer dgit.