If we model a range of real thicknesses for each different material type, or even for each different sheet,we end up with quite a few CAD files.
We have to create a full set of CAD files for every possible combination of thicknesses. For 11 thicknesses and 2 different materials ths is 11^2 which is 121 sets of CAD files. If we never needed to model more than 2 different real thicknesses this might be manageable within a single fileset, but the options and choosing them is still harder to manage. If we go to 3 for even 4 thicknesses the quantity of filesets balloons 11^4 is 14,641.