What size tire for rocky-terrain trails?

Is there some reason that so many of the all-terrain trail tires (not mud-oriented) do not come in sizes bigger than 26" for 12" rims? Is there some disadvantage to tires taller that 26" on rocky and hard packed trails? There are plenty of mud tires up to 30" for 12" rims.

Ok, so I normally just search the threads to find the info I need. Just can’t seem to find where this is covered. My Outlander 500 is set up for the types trails I typically ride in southeastern NC pine forests. Mostly soft, sandy trails with lots of water and mud holes. I currently run 28" Zillas on factory wheels with a spring spacer lift. I have Dalton clutch kit and plenty of power for these tires. This setup works good for me around here.

I have an extra set of factory wheels and I’ve been researching tires for riding a more rocky terrain…Hatfield McCoy, Eastern Tenn, possibly a trip out west, etc. It seems that most of the trail tires for 12" wheels are made no bigger than 26". I recognize that a sacrifice in ground clearance is acceptable when not riding primarily in the mud and ruts. However, I am unsure that it makes sense to go down to a 26" tire that probably only measures 25". Also, feel like I should get a tire that has a similar weight to my Zillas so that I do not have to make a clutch change. Am I on the right track here? Or is there some advantage to 25-26" trail tires that I am missing? I don’t want my outlander looking as silly as a jacked up truck sitting on mini van tires.

I am aware that Bighorns, Dirt Commanders, Blackwaters and Pitbulls are available in 27s. Pitbulls seem nice, but too heavy for my 500. Leaning towards the 27" Dirt Commanders at this point.

tires I like but only go up to 26" on 12" rim:
Roctane
Grim Reaper
Black Diamond XTR