For the vast majority of RVers who do utilize Walmart and other RV friendly businesses on their way to their final destination, it is simply to travel later into the night and leave promptly at daylight.
It's been a few years since we have had to stay at a Walmart overnight but we did several times as we were RVing with our kids and had to make time due to limited days off from work or school.
We've also used truck stops, rest stops, and churches to name a few others. Now with the kids all grown and out of the house, the only locations we overnight are casinos which my DW loves.
As for extending out slides we did it when we were along an edge where they couldn't be obtrusive to other vehicles, when it was hot we would run our onboard generator to cool our rig for a few hours of shut-eye.
I never fret what others think, and certainly do not pay heed to their silly notions about saving a park fee, overnighting is a viable option for those attempting to get somewhere in a hurry and nothing more.