The latest commit message on that file is "Changed lfs_crc to match more common API (...)" so I would assume that they factored out this function specifically so that it could be easily exchanged with another implementation. There are many CRC32 implementations that may be more suitable for the specific microcontroller you are targetting, or maybe you already have an CRC32 implementation in your codebase that you would like to reuse because space is scarce. For the other functions the reusability isn't really given.