Being a scientist myself, I see where you're coming from - but I'll also have to point out that this is a VERY slippery slope you are entering on that thought.
What really IS most useful for society? Many people prefer applied research over basic research, as the former leads to more immediately obvious benefits. However, much of that applied research would not even be possible without the foundations laid down by basic research.
Something similar applies to the field of biomedical research. Back in 2008, a politician from Alaska ranted against "fruit fly research" - why would we even study fruit flies when we could spend that money instead to research medical problems in people, on real diseases that people suffer form? Doesn't that benefit society more? Problem is, much of the basic research that is needed to research new, promising therapeutic options in human medicine needs basic genetic research that is often conducted in fruit flies. There you go...
I'd never say that my field of research is more important than anyone else's. A reasonable approach to science is the following: You'll never now what's going to come out at the end. Famously, Fleming discovered Penicillin when he found mold growing on some test plates he left in his lab, and the mold killed the bacterial cultures around it - pure accident. This sparked a medical revolution that has since saved billions (!) of human lives and made many infectious diseases a problem of the past.
So, no - I'd not dare to evaluate how "useful" any field of research is for humanity. A bit of humility would be called for, I think - and therefore I think that every project on the Gridcoin whitelist is worth of the donation of volunteer computing power in the same way. Consequences stemming from the "utility for society", whether real, perceived, or a carefully constructed publicity strategy, should be reserved for decisions on the individual level ("Which project do I WANT to contribute to?) and not institutionalized through Gridcoin mechanisms.