I vist all the FPSC forums everyday too, usually many times per day - if at all possible.
Most forums I may not post in at all unless I have something I think is of value in some way to say.
As to the showcase forum I rarely post there though as said I may look through many times a day. Personally I dont and would not or would very rarely comment on other peoples work - unless asked specifically to do so.
My own gamemaking is long term, complex and needing of much effort so I only post again when theres something new or I feel is particularly worth showing - such could be months or certainly many weeks in between.
Personally I dont work with FPSC with any view to a quick release of any develoment - it has always been my personal approach that I have a game to make they way I want it to be at a certain standard and will endeavour to make it and release anything only when I am happy to do so. And if I am not happy with it then nothing will ever be shown or be released and so be it.
If there are few posts in that forum then I presume that visitors simply have no comment to make - seemingly one must assume as they have little enthusiasm for one reason or another for whats shown there.
I guess some hot shots of work done with FPSC might generate more interest, but thats not the case with any certainty as pointed out previously above by Benjamin A.
Humans are a starnge lot and theres no accounting for taste.
As to the Why - I guess there are different reasons in each individuals case.
You should not forget either that FPSC has one of the smallest active indie engine communities around. Many members seemingly come and go on a regular basis - some leave others whilst join up. A larger more stable forum membership with long term committment to the FPSC engine would encourage more completed games and more activity in those forums. Too many potential users I believe are lost when they look at it or try it out and dont stick with it - for one reason or another.