Their purpose is to incentivise you to declare war on your neighbours.
You can always try negotiating with neutral/allied states, asking them to allow you to temporarily declare war and take the province and drop. You can then allow them to recapture the province, restore peace, and it's polite to offer them half the loot from the drop (unless it's a blueprint) for their trouble.

(You can also claim that you want to do this if you need an excuse to backstab them. Not that I've ever done that of course.)

No, because technically that negotiation is loophole abuse. The point isn't to give you free stuff, it's to make you go to war with people you might not otherwise. The reason why it's possible to get it under controlled circumstances where both parties agree to it is because the game can't distinguish between regular attacks that get called off early and attacks that were agreed to in order to claim a supply drop.

Yeah that's what I was trying to say.

And negotiating to actually start a war with someone takes just as much trust, since it's very easy to abuse permission to do that.
I'm not really sure where you were going with that comment actually. Or, as a result, where I'm going with this one.

I don't know about that myself, I feel it conflicts with their purpose, but I'm going to leave it at that since we evidently feel differently on that point.

I'm on the lady's side of this one. People play way to passive and peaceful. it is a war game ffs, invade your neighbor, don't just stand around until you're so bored that you fall inactive! If supply drops are ANY help at all to create conflict, make them obtainable by war only.

The intention behind Supply Drops was indeed to promote more active war declarations and to give players some strategic choices.

Supply drops are fine. No changes needed imho.