In the early days of digital design, all circuits were designed manually. You would draw K-map, optimize the logic and draw the schematics. If you remember, we all did many logic optimization exercises back in college. It was time consuming and very error prone. This works fine for designs with a few hundred gates, but as the designs get larger and larger this became non-feasible.
Designs that are described at a higher level of abstraction are less prone to human errors. High-level descriptions of designs are done without significant concern regarding design constraints. The conversion from high-level descriptions to gates is done by using synthesis tools. These tools use various algorithms to optimize the design as a whole. This circumvents the problem with different designer styles for the different blocks in the design and sub-optimal design practices. Logic synthesis tools also allows for technology independent designs. Logic synthesis technology was commercialized around 2004, and since then it’s been part of the standard EDA tool chain for ASICs and FPGAs.
