I'll give you a more concrete experience. We have protocols designed to take advantage of shared memory to allow dma directly from the hardware to the pages backing the file you end up reading from. There are many layers/processes between my program and the driver which ultimately talks to the hardware, and being able to bypass copies for the data is useful. Now the protocol encodes this expectation of shared memory usage within it. We later built a mechanism to take existing protocols and use them across network boundaries, but were unable to utilize any protocols which relied on shared memory. It may be possible to emulate shared memory across the network boundary, but it's hard to do so performantly in all cases. So rather than modify the existing protocol to avoid shared memory, negatively affecting existing use cases, we opted to create a second protocol which was optimized for network use cases.

There are more of these sorts of examples I could enumerate if you find it worthwhile.