Just because something is for sale via aftermarket doesn't mean it is needed, required or an improvement.
IE: Slide out stabilizers, anode rods for Atwood water heaters, digital antennas etc.
You left out refrigerater fans/6-volt batteries/catalytic heaters and a host of other add-ons that make RVing more pleasant. When you have large storage areas in your slide out that is a full slide out then add three or four scrappy kids that weigh well over 200 lbs horsing around, I don't mind having the option to add support for that slide out.
There inexpensive and safe to use if used properly. How many full timers have a factory approved year around living rv? That alone used to void the Jayco warranty.
And think about this, we all know that leveling the refrigerator and or RV is very important but I have yet to see one come with levels from the factory, there all after market.
No problem here, I use them(slide stabilizers) and have for years and never had an issue with them even having the dreaded flat tire while on, nothing happened at all and it was just as level as before the flat using corner jacks.
I doubt there are many if any that don't use some sort of an after market device on there rv.... We each just chose which after market devices fits our needs,which are different for each of us.
Just don't say slide stabilizers will ruin your RV if used properly, because they won't. Anything used improperly is subject to damage!