also to be realistic in a lot of practical situations I/O buffers are reused so at least for the I/O buffer use-case it can be very viable (perf wise, in most use cases) to just zero or rand initialize it once on alloc and then treat it as frozen in all repeated usages (through it does open the issue of bug now potentially leaking previous content of the I/O buffer).

but I guess this isn't just about I/O buffers ;)