Actually, they are useful, despite what anyone else says.
There are lots of opinions for and against . . . and most of those against slideout jacks have never actually used them . . . but just have an opinion about them.
And if the tires go flat . . . your stabilizer jacks will still hold your trailer where it was.
Anyway, I have a set of the slideout jacks that we ABSOLUTELY NEEDED with our former Heartland bumper pull trailer, as the dinette was in the slideout, and when two or more people sat in the dinette, you could feel the whole trailer lean and bounce.
But we are out right now in our new Heartland Prowler 5th-wheel trailer, and I don't believe that we will need them for this trailer as the big slideouts on this trailer don't slide out nearly as far as our Trail Runner slideout did.