Because good as a FN-produced High Power is, unless you know the provenance/round count of the one you're buying used, they can be a bit of a crap shoot, as the forecasted barrel lifespan has been estimated to be in the vicinity of 12,000 - 15,000 rounds, and frames around 35,000, give or take.
The High Power is a great pistol, albeit with some caveats. From a durability standpoint, the fact that they have less mass than a 1911 has led to them inevitably having a more limited lifespan, all things being equal.
While these estimates may be based on forged-frame High Powers (the 1994+ cast frames are thorough-hardened and much tougher), I simply don't know of empirically derived results to substantiate that assumption (that the post 1994 cast-frames are more durable than 35,00 rounds; the barrel lifespan of 12,000 - 15,000 I assume remains the same {except, again, the 3-lugged .40 barrels might be more durable, but {again} there's a lack of empirically-derived data).
Hence there might be a willingness to go with a new clone as opposed to a used FN.
It looks like they're still a bit of a work in progress, though.
Best, Jon