I always wondered that as well. I also wondered why Uberti dropped the magazine plug retention screw in favor of threading the plug and screwing it into the magazine tube so tightly that it is next to impossible to remove. I bet most Uberti owners have never been able to properly clean their magazine tubes after shooting black powder. Miroku uses the retention screw, and I look forward to being able to thoroughly clean this rifle when shooting black powder.
One of the ironies of these "Japchesters", as many of the scornful like to refer to them, is the contempt many folks have for what most often stems from the pain of seeing a Japanese-produced firearm branded with an iconic American name. I think it was easier for people to swallow the Browning brand on Miroku rifles, because the Browning Arms Company has always existed as a marketer or importer of firearms manufactured by others--they were just usually John Browning-designed guns.
So when Browning had Miroku make the 1892, 1886, and 1895, people were just glad to see these guns being made again and to such a high standard of quality. And by the time they did, Winchester's reputation for quality had already fallen; if Winchester had tried to produce them at New Haven, they would have probably been sloppily made.
Since John Browning didn't design the 1873, they never had Miroku reproduce it. Winchester and its successor, U.S. Repeating Arms, just continued to flounder until they finally closed down entirely. Uberti has been the only game in town for 1873 rifles, and they've been at it a very long time. The quality of their rifles has always been pretty good, and prices have remained pretty high. My own Uberti was purchased new a few years ago at an LGS. Better prices are to be had online, but it cost me nearly $1,200 then, and it still required some tweaking to get it to behave like it was supposed to.
Now that FN owns both Browning and Winchester, Winchester has gone the way of Browning--it is a marketer of firearms produced by others. But unlike Browning, people just aren't used to seeing the name "Winchester" stamped on stuff not produced at New Haven, and it is hard for many folks to swallow that. For me, however, Winchester's acquisition was a real boon. Miroku's rifles would no longer be limited to John Browning's designs, and the 1873 became a possibility.
I don't like the added safeties, and some of the other departures on this "modernized" rifle appear at first glance to be neither manufacturing expediencies nor strength enhancements. The Winchester name on my rifle carries no weight with me. The only name on this rifle that gives me confidence is "Miroku"--that is the name that is synonymous with quality for me. Time will tell, but the eventual irony may be that the brand "Winchester", rather than enhancing a foreign-made gun's acceptability to the majority of uninformed Americans, will regain its reputation for quality only because it was made by Miroku.