A loose cable like in the photo above gets caught in the spring mechanism of a pull down folding ladder at the attic opening and frayed.
Is conduit required in attic.
Always check in with the local building code authority.
It will be easier to repair wires if there is a short in the line.
For this reason the nec has protection requirements for nm cables in an attic.
There are a few rules you need to follow but conduit is not one of them.
Damaged cables can cause a short circuit or even worse arcing that will start a fire in the attic.
Conduit also protects your wires from exposed surfaces such as rough bricks in a basement.
Using conduits will ensure that your wires are kept together.
I once knew of a town that required all residential circuits be run in conduit.