Normally, references to blockchain blocks, transactions, their inputs and outputs occupy 32 - or up to 37 bytes (in case of inputs/outputs). For the existing set of transactions residing in blockchain just listing all existing data will require gigabytes of storage space. Many user applications and services, However, require cross-referencing and indexing - like JOIN SQL queries connecting different tables (like transactions, outputs and inputs) with primary/foreign keys, where the keys are 32-byte values. This is both extremely inefficient in terms of performance and index storage space. While it may be a normal practice to use incremental 32-bit indexing, the full identifiers still should be kept, and two different databases created by the same software after some re-orgs will not match by their indexes.