Because thickness is a material property, material libraries become enormous quickly. BCL is already almost unusable for constructions.
Thickness is an extensive property, it should belong to a layer in a construction. Materials should encapsulate intensive properties only. We might be too far down the road to solve this in E+, but it would not be that tough in OS.
This needs to be coordinated with and targeted at the BCL. There only needs to be a single entry for 140# concrete etc. The same goes for private libraries.1 vote