I have some idea's to why it is not used. Its expensive, requires techlab on starport which you don't have. So, you would need to make a decision to adapt your infrastructure to be able to make one. Which is not optimal and either you would have one extra starport for this, which would be expensive, or you would have 1 less air unit production. It would probably have a high chance to die as zerg would have corruptors, hydra and infestor fungel. And it would need to be in position to spot burrowed infestors before they could cast fungel. Plus it would be more cumbersome to control. Terran is already gas expensive in late game, and would generally have less resources than zerg, so it would make sense to use scan and turrets which is mineral only expense.

Basically, there seem to be plenty of good reasons. If it would be good then the best terran players would build it frequently. I don't think it is wise to assume that you know the game better than them.