when you mount a bin/cue image in PowerISO it shows both files and you can mount the bin without the cue, so my question is do you really need the cue file and does it matter as long as you're not burning it onto a CD or DVD?
You don't really need it, though .cue files often contain instructions for burning programs, like burn speed. It would be safest to just use the .cue file when burning that is. It is not necessary though.