I think the ramps and position of the teeth on the cogs are designed to work together so if you start mixing and matching they won't line up and it'll screw up the shifting. Plus the larger cogs are often mounted on a single carrier (and I think some SRAM cassettes are even one-piece).
I think the ramps and position of the teeth on the cogs are designed to work together so if you start mixing and matching they won't line up and it'll screw up the shifting. Plus the larger cogs are often mounted on a single carrier (and I think some SRAM cassettes are even one-piece).