Hi Stabby_Dave,
Cargo racks have some uses for explorers in the black besides salvage.
Even if you aren't equipped with a repair limpet controller yourself, you can synthesize limpets for the Rat repairing you if things have gone that crazy for you. But you do need the cargo rack to put them in for a moment before you drop them. I'd say this more important on a expedition, where co-operation is key to success.
Also, it is still possible to find ocupied escape pods you might want to rescue.
One other use for a cargo rack in an explorer, is to "trim" your jump range. Maximum range jumps use an increased amount of fuel. You are pushing your FSD to the limit, and it becomes ineffcient, burning excessive fuel. There is a slider in the galaxy map that lets you increase the virtual mass of your ship if you have unused cargo space. If you add just 1t of virtual weight to your ship, your jumps will be slightly shorter but more fuel efficent.
If you go out exploring in a non-exploration ship (a fighter for example) this can be a very useful trick, for example if the ships fuel tank is very small (or if you've dramatically reduced your Asps fuel tank to save weight/gain range), trimming the range to stay fuel efficient may allow you to get two jumps from the tank before you must refuel. Good for those times you hit a run of unscoopables.
That said, a cargo rack is far from being essential equipment, pop one in if you've got a spare slot, the rack itself weighs nothing.
Good luck on your trip.