Hello. I think the answer comes in two parts. I heard much, but
this makes the most sense to me. If I'm incorrect, others in the know will post.
Single-action automatics are not as popular with the majority of folks buying handguns. My impressions are that younger officers as well as folks wanting an auto for defense/sport/whatever prefer either Glock pistols or others that have the conventional DA/SA trigger mechanism or DAO. The see these as more "safe."
Single-action autos are popular with many who actually shoot their handguns for recreation, are serious deciples of self-defense, or compete. There can be much overlap.
Having said that, who would argue that in the US, the 1911's not the most popular single-action auto around? Obviously, it is and by a majority. Sales for the SA BHP were relatively low compared to these other nines and most wanting a SA auto, bought some kind of 1911.
Enter the frivolous lawsuits designed to put gun makers out of business and Browning decided no longer to import these pistols.
FN IS importing them, but only in lots of around a thousand or so. When those are sold, they import another similar-sized lot, at least for now.
The BHP is and has been used the world over, but in 9mm. I think that forty is popular primarily in the US, but even here, I'll bet that the 9mm BHPs outsold them. I am guessing here and have no figures, but I believe that unless shown otherwise.
Thus, for cost basis per gun, FN's doing 9mms now. I have heard that they "may" make some more forty HPs in the future depending upon sales of the nines, but that's a rumor unless someone else has better information.
Best.