[luma]

How so?

[CamperBob2]

4-bit values (or 6-bit values, nowadays) values are interesting because they're small enough to address a single LUT, which is the lowest-level atomic element of an FPGA. That gives them major advantages in the timing and resource-usage departments.

[iAkashPaul]

Reduced memory requirements, dropping higher precision IP blocks for starters