Quote Originally Posted by The Glyphstone View Post
Theory 1) The Old Ones built in the tech-dependency as a means of keeping them on a leash, and a hard-cap to ensure they couldn't evolve past their built-in constraints.

Theory 2) Bio-weaponry along the lines of the Tyranids was beyond the Old One's capabilities to reliably engineer, so they went with the next best thing of genetically hard-wired technical knowledge.
*shrugs* It's not inconceivable that sort of explanation might hold up for a few thousand years. It's just a very contrived, awkward and fishy long-term explanation.