Well, it's also keeping cost down. But makes sense, use what works, keep cost down let the DIY'er, DIY.
By the way, the Alps is available with different length shafts. The ones I got from Mouser did not need cutting. Mouser had, at the time I bought, more than one version of the 100K duals.
Im afraid that, personally, I wouldnt hear much if any difference between the Alps and TKD (the basic model atleast). The "better" TKD is close to $100. The basic model is over $40, 3.5X what I got the Alps for. Doesnt mean it's not worth it to others. Just personally, I've been happy with the Alps, tracks well, sounds fine and is inexpensive. For me, the PEC at around $35 or so would probably be what I would try if I were to change. Supposedly a very nice pot for the price if you get a "good" one. The IF is the problem I think. Ive read that SOME can be scratchy and poor low level trackers.