Why do dollars or euros or yen have value, they are just imaginary tokens backed by debt. They have value because certain groups agree to use them to exchange other items of value, that's it. So if any currency gets into the hands of a critical mass of users either locally or globally, it will become valuable. Of course it needs to be secure, fast, and ethically sound for people to prefer using it over a similar competitor.

How a currency is brought into circulation has little to do with its value.

There is a mechanism built into Gridcoin called "rain" that allows a research project to give additional rewards to people doing the work, but as commercial enterprises don't do distributed computing at the moment it's not much used.