Here is The issue; now every derailleur chain is bushingless , the edges of the roller rides on a flange
made by punching the holes in the inner link plate .. one coming in partially from both sides..
Pin tides around inside..
steel side plates have been made thinner in order to make a denser stack of cogs, 'speeds' in a limited width..
so a thinner piece will wear through where a thicker one will take longer..
this is an idealized diagram ..