At least with Primecoin, I can go to bed knowing, we made progress for future benefits. What can these numbers do?
I seriously doubt these prime numbers we find have any purpose at all, now or in the future
There not prime numbers, they are Cunningham chains.
http://primes.utm.edu/notes/faq/why.html
Some say they are looking for the mathematical fingerprint of God, like Carl Sagan wrote about Pi in his book Contact.
Or http://rense.com/RodinAerodynamics.htm
Perhaps they are just nutters.