Well, Les, because the cable is not expensive relative to the alternatives in small quantities. At a buck a foot you're getting 4 extremely high quality OFC copper 23 or 26ga teflon dielectric cables pre-configured in a precisely wound 4-conductor braid (a different configuration than 2-conductor twisted pair, although they both are technically the same solution to the same problem). The Canare variants are half that price. You could probably buy one or the other with a quick trip to the local music store.
The Mogami product is extremely well extruded and of known quality. I don't know what research you've done with regard to extruding wire and cable, but one of the (many) issues is the consistency of each copper strand, for example. Keeping the diameter constant over a length is not trivial and varies between factories.
There is potential for inconsistencies to affect signal integrity, although I can't say exactly how much. Suffice to say that it is not a given that each strand will be within, say, 5% of 0.1mm over any significant length. And that is just one aspect; there are issues with purity within the factory, with the hardness or softness of the copper (or other material), the quality of the PTFE (which is made worldwide now as the patents have expired and methods are known, not just by DuPont), and so on.
The best means for us mere mortals is to buy from known good suppliers, because you won't get that information from the cable manufacturer, if even that is known. For example, we don't know who makes the Canare cable, but we do know Mogami makes everything they sell at their owned factories in Japan, down to each strand of wire itself.
In my mind, eliminating possible inconsistencies is key to experimenting. So, when we have an opportunity to use a product that suits our needs, is of reasonable cost, and is made better than I myself can make it, I say take it.
Were it simple twisted pair, and if you could have a suitable single 23/26ga cable shipped to your house for 25c (or 12.5c for Canare) a foot all in, it might be different. Also, if you're buying bulk quantities, the economics might change.
I don't know how experienced you are with manually braiding cable, but it's difficult for me, at least, to get good consistency and becomes complicated with a cable length longer than about 4 or 5 feet.
I don't find it difficult to cut and remove the jacket, especially if I'm not concerned about nicking the served copper shield that Mogami prefers (despite it's higher manufacturing cost) for these two variants. Because it's not a braided shield, it's very easy to remove (just unwind it), leaving the 4-conductor braid in excellent undamaged condition for termination to your favourite RCA.
For a quick-and-dirty primer on shielding of cables, it's hard to beat this pdf from Belden:
http://www.belden.com/pdfs/Cable101/Shielding.pdfI agree that sold wire construction may be the preferred configuration for audio, but then again a little experimentation comparing the shielded and unshielded varieties of the same cable has value to me. One variable at a time, so to speak.
Correction (edit 18 Dec 2011)
The Mogami cable part#'s I've mentioned use Cross-linked Polyethylene (XLPE) dielectric, not Polytetrafluoroethylene (PTFE aka Teflon(R)).
Off topic discussion moved here:
PTFE and Teflon (R) 
3 Jan 2012