When would one use a 22.5 x 9.00 rim?

Hi, I asked a variation of this question in a previous post but thought I'd ask again as it may have been buried in the post.

When would you use a 22.5 x 9.00 rim (as opposed to a 22.5 x 8.25)? I see in the Accuride catalog that it is listed as a "heavy load" application (10,000 lbs vs. 7,400 lbs). Is this a common size?

Can anyone tell me who uses a 22.5 x 9.00 and under what circumstances? (Is it just to control sidewall flex or are there certain kinds of hauling scenarios where one would prefer a rim that can handle a heavier load.)

On the same note, if someone can help explain how the 10,000 lbs vs. 7,400 lbs max load works that would be great (e.g. 7,400 x 4 = the maximum load on the axle?).

Any answers would be greatly appreciated!