"Specular maps" is an unfortunately ambiguous term in the industry.

Let's break that into two variants:

A map that shows actual highlights, which are the result of light source position, size, color, geometry position and orientation, material behavior, and camera position, ... is bad.

A map that describes material behavior or properties (i.e. shiny here, not there, smooth here, rough there) ... is good.

The kind of specular map that is good does not show highlights. It shows where the potential for a highlight exists, and to what degree (reflectivity level and blur).

Further, the good kind falls into two levels - micro and macro.

Micro level details, such as the shape of poors, the tiny crinkles of skin in general, are not needed to be in a specular map. I can do those with more precision, flexibility, and detail in a procedural.

Macro level details are great in a map. This would be information like:

Forehead area - medium size poors, lots of krinkle - shiny.

Nose area - large poors, almost no krinkle - shiny.

Upper cheek - tiny poors, medium krinkle - slightly shiny.

Lower jaw - no poors, small krinkle - no shine.

I have never seen anybody make such a map for any Poser figure. 

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