Of course, that was in back in the days when an entire platform from hardware to userland could be exclusively optimized to utterly and comprehensively smash it in just one very specific and precisely targeted market. Which is, of course, exactly what the iPhone was.
Just as the first Apple Macintosh a decade earlier eschewed not only multi-user, multi-process, and even a kernel; every single bit and cycle its being being exclusive dedicated to delivering a revolutionary consumer UI experience instead!
In comparison, NeXTSTEP, which ultimately became iOS, is just one great huge glorious bodge. “Worse is Better” indeed!
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Honesly, poor Be was just really unlucky in timing: a few years too late to usurp SGI; a few too early to take the vast online rich-content-streaming world all for its own. Just imagine… a BeOS-based smartphone hitting the global market in 2000, complete with live streaming AV media and conferencing from launch! And Oh!, how every Mac OS and Windows neckbeards would’ve screamed at that!:)
Someone else pointed out that BeOS allegedly had "quality and security" problems in general (I myself have no idea), so that may indeed have led to problems down the line, whereas BSD was pretty solid. But I agree with the OP and don't think POSIX security in particular is much of a factor today.