SJs are cheap and plentiful on the used market, and not much more when new. That's why we have them: temptation. The rest is just portability and placement that lends them to be good chimney holders if you lack a cement slab to set it on.
I have one SJ. Drove too far to get it and give $5 for it because it had a wood handle. Abused it by ignoring it until the kids knocked the lid off the deck and left it there for 2 months. Maybe more. When I went to retrieve it, saw the lid was dented in. I turned the lemon into lemonade by installing a Weber smoker thermometer that not only concealed the dent but now looks nicely flush, almost. It's currently part of a mini WSM.
But that's not the kind of answer you're looking for. This one might not be, either.
When I start charcoal on the grill I'm cooking on, I invariably get ash on the Performer's table when dumping coals into the kettle. It's not that my aim is bad, it's that ash falls though the chimney as I pick it up and tilt. For some reason, if/when I use a different grill I make a point of shaking it first before carrying over.
So that may be the most arcane reason you'll read.