Many of us are actually post from our computers and from our iPhones/iPads/whatever. When I travel and get a cancelled flight or staying in a boring location, I might spend a few hours on MR with not much else going on, just probably some light emails, work stuff, magazines, coffee, newspapers, TV.
When working, then it's slightly different. I have a computer that I don't use for work at all. I often have MR running in the background there.
But don't think that a few posts per day means that we are students, unemployed or IT guys!