Use of the goop keeps the aluminum wiring from oxidizing and creating a high resistance connection. The problem with using aluminum wire for equipment with a high current draw is that it still gets warm, expands, deforms slightly due to its' plasticity at elevated temperature, then keeps that shape when it cools. It is now ever so slightly looser a connection than before. Over time, the connection gets looser and looser and eventually becomes a high resistance connection, and a fire hazard. If you must use aluminum wire to connect your machines, protect yourself by re-tightening all connections on a regular basis, and get someone in to do an IR scan of your connections to make sure none of them are running at a higher temperature than they should, because a connection running at an elevated temperature won't be visible until it starts to burn the insulation off the wire.