That's not always true, you don't need to have two full copies of the library at all times. See Geoff Collyer's explanation here: http://harmful.cat-v.org/software/dynamic-linking/ (but note that the memory use that he cites may not be that relevant).
I am also not convinced that this is a significant impediment for all workloads. For a lot of applications, the time wasted due to inefficient cache use is a fraction of the time spent waiting for stuff to be delivered over the network.
I am also not convinced that this is a significant impediment for all workloads. For a lot of applications, the time wasted due to inefficient cache use is a fraction of the time spent waiting for stuff to be delivered over the network.