If your software is super-ugly then, yes it might hurt you. If your software is UI less, then obv no, you dont need a screenshot.
However if your software has a slick interface and is very appealing it might actually help.
There is a pit fall in software screenshots though, you should avoid.
A full window screenshot scaled down will be totally worthless.
You can do a partial screenshot, or whole screenshot utilizing a magnifiying glas on top of it like here:
If there is some feature in particular you can describe, and suppport with a partial screenshot then that should work.