why does TTLV encoding in KMIP require padding?
The padding in KMIP is present only when data is converted to TTLV format, which is a binary representation of KMIP data. TTLV padding exists to "provide optimal alignment for both 32-bit and 64-bit processors" according to the kmip specification. It's generally easier for a CPU to load memory when it's aligned to certain byte widths, especially when the CPU is doing work in parallel.

see section 9 in the kmip 1.0 spec:
https://docs.oasis-open.org/kmip/spec/v1.0/os/kmip-spec-1.0-os.html#_Toc262581260

wikipedia describes how "there can be substantial performance advantages from using aligned data" on x86 cpus:
https://en.wikipedia.org/wiki/Data_structure_alignment