Quote - Antaran-
There may already be a feature request about this over at DAZ. There was some debate in the DAZ forums a few months back; strangely there didn't seem to be much interest in specular lights; everybody was blabbering on about cloth simulators and fluids solvers when it came to "must-have" features :)
If you open up a request let me know; I'm part of quite a few Carrara groups and I'll definitely spread the word!

I found this feature request and have already added my support to it: https://bugs.daz3d.com/view.php?id=36350

The more supporting issue notes there are on the feature request, the greater the chance that DAZ will pay atterntion and start working on it. So please add your supportive comments and spread the word to get better promotion for this request.

While I see the resons for people wanting to have cloth syms and fluid syms rigth there in Carrara (animations mostly), I think this issue is of equal importance: being able to animate requires the ability to animate faster and specular-only diffuse-only lights are an essential part of that optimization. I think this should be made clear both to DAZ and to Carrara users.

I also have a bug report about GI ignoring don't-cast-shadow settins, so please add your support to it as well, if you believe it should be fixed:

https://bugs.daz3d.com/view.php?id=39886