thing is directed graphs have loops in them, but I'm a bit unsure what it would mean to plug the output of a blob directly into one of its inputs. for instance suppose you had \\(\Phi : X \nrightarrow Y\\) and \\(\Psi : Y \nrightarrow Z\\) – you could tensor them to give \\(\Phi \otimes \Psi : X \times Y \nrightarrow Y \times Z\\) – and maybe if you "loop" by plugging the output \\(Y\\) into the input, you'd get plain old \\(\Psi\circ\Phi : X \nrightarrow Z\\)? but I'm just speculating here.