Do I have to put the 120 volt wiring in my attic inside of conduit? I don't recall ever seeing any wiring inside of conduit in an attic but I'm not sure.
No, conduit is NOT required in attics. Not unless conduit is required in your area.
There are other factors involved in wiring in attic spaces, but your question is a bit too vague to go into that.
You only have to put the wiring in conduit, if you have to protect it from physical damage. i.e. If you're pulling individual wires, or cables are run in such a way that protection is required.
Without knowing what type of cable/wire you're installing, it's difficult to be more specific.