I think the main scenario that justifies structure spam is when you already have a fair number of somewhat high-level structures that are busy fending off opponents, considering that you don't want to bring them offline for significant periods of time. Upgrading your research centers serves as a small upgrade for all related structures, which is great if you have a lot of them.

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram