I took in a Remington R1 TB (Threaded Barrel) 1911 on trade and asked the same question... Why they heck are these even sold in Canada??? The shorter Commander lengths are allowed here... The only thing I could come up with is people think they look cool, or you could use it to add a compensator. I looked for compensators and they are not easy to find in Canada. So, I'm left with the notion people must think they look cool.
I think the ultra high clearance sights look goofy, so I swapped them with nice adjustable fiber optic ones. I don't mind the looks of the extended barrel and black threaded cap. Now with the regular sights and a threaded barrel it's makes even less sense to it's existence. LOL!
It turned out to be my best shooter in 45ACP beating out P220, 97B, and other 1911's so I don't care anymore.
Good thread though!