Aside from idscout's points, wondrous things like move & reference semantics minimize the the need to impose extra copying... and of course you can probably use

Aside from idscout's points, wondrous things like move & reference semantics minimize the the need to impose extra copying... and of course you can probably use typedef/aliasing tricks to go over step further. Given the desire for the use of secure memory (hardly unique to the library), the usual overhead involved with network PKI (even if you use a hardware accelerator and rdma-type networking, left alone the CPU), and the common practice with networking code in general to copy data in to buffers (particularly with asynchronous IO code), I'd hardly call this a huge design mistake.