Modern Intel CPUs have an instruction specifically to compute CRC. This instruction is easily consumed through a C++ intrinsic, literally in one line of code. You can't do any better than that, no matter what you use.
[Intel's CRC32 CPU instructions] uses different inputs to the CRC32 algorithm (known as the polynomial) which is apparently more robust, and is used in networks, filesystems, that sort of thing. It gives different results to the "standard" polynomial, typically used in compression.
They would have to go back and recompute all their existing stored checksums.
Replacing a function with a faster implementation is trivial; its just another deployment and we do several of those each week. Changing data format adds operational complexity - two codepaths need to be run and maintained and we increase system load and lower response times for the duration. (The data format is versioned, so that's easy - no architectural problem there).
Its totally worth doing if you need to, and we're not afraid of that, but you don't do it on a whim - it takes proper planning and testing and needs multiple people involved.