Considering pipelining up front rather than later on can improve timing closure. Adding pipelining at a later stage to certain paths often propagates latency differences across the circuit. This can make one seemingly small change require a major redesign of portions of the code.
Identifying pipelining opportunities early in the design can often significantly improve timing closure. It can also improve implementation runtime due to easier-to-solve timing problems. Reduced switching of logic improves device power.