Along with what picketpin said, which I do agree with by the way, I gotta ad a bit.
If they can tool up for the 17 Hornet, which has little use to me, why not the 444 Marlin which would be far more useful in the hunting fields!!! Further, they have tooled up for other cartridges whitch are basically useless to many.
The .17 Hornet is a brand new cartridge so that alone will get folks attention as opposed to a classic such as the .444 chambering. Sadly, while quite formidable, many do dismiss it as a classic and see no modern appeal. It also gets quite overshadowed by the .45-70 chambering. Marlins are a perfect example - how many do you see/hear discussions about in one chambering as compared to the other?
Now on with your methodology of substantiating the need for a .444 #1. Why when there's other chamberings that are far more useful?

Look at just the limited chamberings in the #1 line. Plenty of others that are more versatile/useful than the .444.
Now this "many" you mention...well, as picketpin mentioned, the #1 is a niche market so there isn't a "many" compared to other styles, and models of rifles. also, as he stated, it's mostly older folks that are those buying the #1's. Have even had Ruger sales folks tell me the same thing, small market, older buyers, etc. Those are not generally the ones with a lot of disposable income or the drive to buy, buy, buy all the time. The #1 folks however are in general, the types that take the time and make the effort to properly care for their #1's. Hmmm, maybe that's why used ones are dar less common and they're most always in excellent condition when they are available.
Would such a creature sell? Perhaps but it would do far better in a blued/walnut configuration than a stainless/laminate style, one that's completely unnatural for the design and classic styling of the rifle. Maybe a good indication of this is the stainless ones were dropped while the blued ones remained.

However, is such a creature is THAT important, re-barreling isn't a difficult task for a good gunsmith that knows what they're doing.
Oh, and if you know where to look, brand new stainless #1's are still available.
