Why does copper thickness matter during PCB production?
Copper thickness and widths of traces should be the same as eventually, both will affect the carrying capacity in a PCB—the longer the widths of traces, the higher the current capacity of a PCB could be. In other words, a higher copper thickness may lead to a higher current capacity of a PCB. If you are looking at an electronic product with high resistance performance, the demand for copper thickness will be higher.
 
Please see the recent PCB manufacturing information as follows:

Actual Product Photo:	Specification:	Stack-up:
	Layers: 2L Thickness: 1.6mm Finished Copper: 10 oz Board Size: 98 mm * 159 mm Surface Finish:  HASL Min. Trace / Space: 40 mil/  28 mil Smallest Hole: 0.88 mm Special Specification:     Filled Copper PCB
Surface Cu Thickness: 10oz(350µm) Solder Mask