There are two places where you might need them.
- Asphalt site on a hot day. Your jacks can sink into the asphalt. Some RV camps with asphalt require pads.
- Sandy muddy spot where the jacks can sink in.
I found a sheet of 5-ply 3/4" plywood in my friend's back yard and traded him a beer for it. Then I cut 4 1-foot squares and keep them in a basement if required.