Can't tell if srs or not. Most likely these people are mining for the FUN of it. For a lot of us mining for bitcoins, no matter what the difficulty is, draws a form of primal satisfaction similar to watching your HD defragment. 
This
Also I don't pay anything extra for electricity and my computer is on all day anyway so why not have it fire up mining when the system is idle?
I even mine on an old pci card also that I found in my old stuff, it manages like 2mh