If you're going camping in a place where weather is unpredictable, bring a tarp to avoid the inevitable surprises of wild outdoor life. A tarp can help keep the bottom of your tent nice and dry as well as free of mud. If you are hiking and you get the underside of your tent wet and muddy it may be difficult coming up with an opportunity to clean/dry it. If you only have time to air your tent out at short breaks, then there is no guarantee you will be able to air out both the top and bottom of the tent. If your tent is dry when you take it down, you save yourself the effort of drying it on the move or when you get home. Putting down a groundsheet can also help you visualize your tent placement and easily move to a different location if your current spot doesn’t work for you.