Those type stabilizers come from the era when the first sliding rooms became available on RV trailers. We called them tip outs or pull outs as it was all done by hand. Early models didn't have any type of gear or pulley system that would hold or move the tip out against the wall of the trailer.
So we used the stabilizers.
Back then there were few gravel surface campsites...no concrete..... mostly just dirt.
When it rained it was all but impossible to keep the trailer stabilizers and the slide out stabilizers at the same place as the trailer will always sink in the mud.
Fast forward today with gear and hyd operated slideouts that hold them tight against the exterior wall eliminates the need for them.
Use them if you want but just be warned I've seen a few slideout repairs with holes punched in the bottom from a stabilizer.....even when they were required and we had to use them.
My last two RVs came with 13' slideouts. One was gear operated and the other was a hydraulic unit. Both kept the slideout tight and in place.
'03 Dodge 2500 Cummins HO 3.73 NV5600 Jacobs
'98 3500 DRW 454 4x4 4.10 crew cab
'97 Park Avanue RK 28' 2 slides