Why perfusion in organ on a chip?

Adding perfusion to organ on a chip devices adds a layer of complexity, so we need to see clear added values to introduce flow in an in vitro system.
Here are a few examples of why perfusion could be useful in organ on a chip.
Any comments or questions? Please feel free to leave them in the comments.

organ on a chip, tissue chip, micropysiological systems, mps, microfluidics, in vitro, consulting, azar innovations