Seimitsu is not as popular as Sanwa is… That’s all there is to it.
And FYI, Hori DOES offer joysticks that have Seimitsu parts. They’re just not large production runs like the HRAPs with Sanwa parts, and, for the most part, most HRAP SE’s are aimed at the Japanese cult market for 2-D shooters which (surprise, surprise) is the one niche that the XBox 360 dominates! It’s a far smaller niche than fighting games but it’s there… and it’s a genre that the LS-32 excels at although those of us who use Seimitsu joysticks all the time know they’re more versatile (in general) than the Sanwa JLF OR the Korean joysticks (from what I’ve heard).
Qanba also offers joysticks with Seimitsu parts but I really can’t answer if they’re offered for wide market or exclusive to ArcadeShock which is the only place I’ve seen the Qanba SE’s at in the US.
The JLF is good for more modern, slower-paced polygon-based fighters but not so good for older-style hand-drawn, faster-paced sprite-based fighters like the Capcom CPS-2 fighters and SNK’s Neo Geo series. It’s not as quick and as responsive as the LS-32 or LS-40 nor does it executive tap-tap, dash particularly well.
The HRAP’s with Sanwa parts were very popular and set the standard for the rest of the pro-level joystick manufacturers to follow. Unfortunately, they’ve done this to the near-exclusion of the other part manufacturers.
You are not going to see Happ or Korean style-parts in Japanese-based joysticks UNLESS they redesign their parts to fit in Japanese stick bases AND fans support those parts. The sad part is that more fans will NOT support redesigned parts by alternate part manufacturers unless they get released first! The broader part of the market is NOT like modders and they will neither mod their stick bases to fit alternate parts because it’s too much hassle for them to figure out how soldering irons and Dremels work, OR they just don’t want to pay for parts and/or labor to get their sticks modded for Happ and Korean parts.
The physical reality is Happ parts will NOT fit into Japanese stick bases… They’re just too big and bulky. Korean parts can fit but only if the Japanese stick bases are extensively modded. That requires more cutting, filing, and resizing of holes to support smaller 28mm Korean buttons as well as mounting Korean joysticks than it does to modify Tekken 5 joysticks to fit Seimitsu joysticks OR install true 30mm arcade buttons into licensed HRAP bases. I’ve modded three Agetec bases to support Japanese parts but I realize the level of work that I had to do to accomplish that is beyond what most people will commit to… Most of these people will NOT learn to solder NOR take the time to do proper measurements and drill into faceplates to mount alternate joysticks in HRAP’s or Mad Catz TE’s. Certainly soldering is cheaper to learn than buying PCB’s all the time that support non-soldered connections. IF you mod just two joysticks with a decent $40 soldering iron that certainly more than pays for that soldering iron… PCB’s with non-solder connection terminals cost on average at least an additional $20 than PCB’s that require a modicum of soldering.
The bigger part of the tourneys are dominated by sticks with Japanese parts. The larger part of gamers who buy Happ parts are people who are into retro games besides fighting games and those who want to recreate the experience of American arcades. The Happ buyers and enthusiasts are a smaller minority than the crowd that buys Seimitsu parts. There are far more Seimitsu fans than there are Happ and Korean part fans put together – at least in the US market… and probably at least 3-5 times of the people who bother to buy new parts for their joysticks will buy Sanwa over everything else because that’s what’s already in their joysticks and that’s what they’ve been led to believe is the best brand of all. Most of these people will never experiment with any other brand of parts let alone less-expensive clones of Sanwa (or Seimitsu) joysticks that are generally just as good as the branded joysticks!