The compute server generates output on a note-by-note basis in real-time, but it needs to analyze the input note patterns as wholes. This synchronous output but asynchronous input would be very cumbersome to achieve using a standard plugin architecture or MIDI communication, because an entire play cycle would be required merely to transmit the notes to the compute engine where they would there require reconstruction into the original patterns.
Max together with OSC also enables transmission of arbitrary instructions between Live and the computer server. Therefore the Max for Live device can contain GUI elements that directly control the compute server, in this case the assignment of selected MIDI clips as musical inputs to the algorithms.
Finally, Max and OSC facilitate routing of the compute engine output back into Live to be rendered into audio and mixed/synced with the currently playing Live scene.