Why should null have any extra passive income? You already have more valuable resources and rats to begin with.
And yes - the mechanics favour the defender. But that doesnt mean you cant harass and disturb their industry and resource gathering. The SOV changes back then where meant to stop the senseless taking of endless space for no reason and with the sole purpose of ‘renting’ it out again. You are not supposed to take space if you cant really use it. But there are more reasons to go to war than just resources. Roleplay a bit and you can find tons of reasons why your neighbour deserves a proper spank.
The not making isk is an organisational problem. If your corp/alliance doesnt have a system in place that keeps you afloat enough at all times then something should be changed there.