Just for the hell of it.

#1 rabid Faerie fans have been around for a lot longer than D&D or Disney, and there have always seemed to be people fascinated with them, and wanting to do pictures of them en.wikipedia.org/wiki/Cottingley_fairies why? IDK

#2 the market hates a vacuum, new figure means new opportunity to create new products for the figure that people will want because they have the figure but have no content for the figure yet. the creator of the figure doesn't have to pay merchants to support their figure because the merchants know that fact. and on your second point in that question the time frame, its pretty spread out as others have alluded there have been two versions of poser since P6 (3 if you count Poser Pro)

#3 The secondary morph package thing? Well that started out based in part on people's desire to have more and more morphs in a figure, but complaining that the figures have gotten too bloated, you yourself champion the one figure fits all concept well that means more morphs generally. and with V2 there was no way to expand the figure beyond it's base morphs easily. Yes there were aftermarket morphs and they could be loaded with Morph Manager and by other means but it wasnt a simple one click solution (Don't get me stared on people's dependence on one click solutions). as far as why people sell characters based on those prepackaged morph channels rather than create their own. the answer is simple, conforming clothing support, if you use stock morphs than more clothing will fit your character and more people will buy the character, yes there are a number of merchants like Blackhearted who create their own character morphs from scratch, but try to find clothing that will fit those characters and you will see why everyone isn't doing it. That's not to say this will always be true, Morph transfer to clothing has come a long way since the Tailor. Dimension3Ds Morphing Clothes is a perfect example of how far its come. also we have dynamic clothing which doesn't have to be concerned with morphs.

#4 if you are on the internet and don't realize that sex sells now than I don't know what to tell you. and btw yes there is a realistic Police Uniform for V4, I created it. www.daz3d.com/i/3d-models/-/real-world-heroes I like doing realistic clothing, but I can tell you that it's not as lucrative as the "Whore Clothes" which is why you see so many of them and less of the realistic stuff.

#5 I'm working on it. (;  But I also like to do the female stuff. and again, the female stuff sells better so guess what most merchants focus on?