We always tarp with an overhang on all sides. Keeps tent dry and overhang is good for kitchen, and keeps coolers etc dry and in the shade.
Also hunting western Washington during the fall your most likely breaking camp in the rain, so having the tarp up allows you to break camp and put everything away ''dry" and the last thing put away is a wet tarp.
Yeah I have been tent camping 20 years now. Just bought my first wall tent but had canvas Trek tents. If you do some reading most guys are tarping their tents wrong.

The tarp and I use the white ones, should only touch the ridge of the tent. Not the whole roof. This allows for dead air space between the fly tarp and the canvas which keeps heat in and cools during hot weather.
I buy the tarp to hang 2ft each side 12 inches in back and 3ft in front to allow for a dry entrance.
I use bale twine or light code to pull the fly really tight with a good slope. Rain, wind stays bone dry.
When its time to leave you have a free floating fly to stay dry and work under taking the tent down.
I know some guys who swear by clear plastic to slide snow off.
Only been in heavy snow once when I first started and the tent was crushed.
The tarp ,fly protectss the top as others have said, from sun, dirt, pitch, and sparks.
Most manufactures recommend you put a fly over your wall tent.
Yeah I know lots of folks dont. Everyone has their way.