If you're just on an overnight stay and the forecast is good, there's no need for a tarp.
If you're just on an overnight stay and the forecast is good, there's no need for a tarp. However, any more than one night and I put up a tarp for protection from rain as well as wind. I typically put it over my picnic table, however, the gale at a campsite on the shores of Lake Superior once had me positioning it horizontally in front of my tent to break the wind.