Most cabinet smokers are insulated and offer some form "set and forget" mode, even if it's from add-on electronics. I think that appeals to comp cooks who like to cook low-and-slow and get sleep.
While there are a lot of stick burners out there, I see very few of them in use for low-and-slow cooks. Most of them are hot-and-fast cooks, or they're for cooks who do one competion per year. I'm not saying that there aren't exceptions, but that's the trend I've been seeing at comps in Missouri, Illinois, Tennessee, Mississippi, Alabama, and Georgia over the last five years or so.
Of course, just because something is a cabinet (vertical) smoker doesn't mean it isn't also an offset, and not all offsets are "horizontal pipe" smokers. There's the Brethren/Klose MOAB, the Yoder Stockdon, and my own personal pit, the Beast from Lonestar. I'm pretty sure Ritch has a couple of vertical only stick burners in addition to the Rebel cabint if memory serves.
I'm not sure if I have a point this time, except that insulated cabinet smokers that run on baskets, gravity, or pellets allow for sleep. Horizontal stick burners are still used a lot in comps, but mostly for hot-n-fast cooks from what I've seen. Things change...
dmp