Maybe give it to an ally?

PJI?

Phase Jump Inhibitor

there is also the reason that if you over extend yourself, either geographically or economically, you can scuttle a planet to reduce the strain.

for instance, if you expand too quickly early-mid game, and dont upgrade your planets, you can actually create a negative income situation. in this case, you would want to scuttle a planet to start making money again.

also, if you take a planet that is within enemy or allied territory, and you cant or dont want to maintain control of that planet, you can scuttle it.

im sure there are other reasons too why you would want to scuttle a planet... perhaps an idea for a mod or expansion is, when being overwhelmed, to adopt a Scorched Earth policy, leave a booby trap on the planet, evacuate the population, get a bonus of some sort (nearby planets get raised alliegence and credit income boost? or at least get some sort of one-time resource boost due to the resources and tech saved by evacuating)

and when you leave, and the enemy tries to colonise, the 'bomb' will go off, all your structures in orbit will detonate (mini big red button) dealing damage to nearby ships (and denying bounty to the attackers), and the colonisation will fail, enemy aliegence will decrease, the colonising ship could be damaged (colony caps) or destroyed (colony frigs), and colonisation will be delayed by... 2 minutes?

sounds like a good idea to me...

but yeah, atm i think there are only a very few reasons to scuttle a planet

If your planet has an income penalty, you can grab all the extractors, build to the limit, then scuttle.

I don't know if it's a bug or not, but if you scuttle a planet with low output from the extractors (because of the distance from your homeworld), the output goes to the full value.

Useful if you have one of the mods installed. For example barren planets have a huge metal output but usually a large negative income. Colonize, build extractors and refineries then abandon = massive metal income.

@ Fuzzy Logic: Shhh...that's supposed to be a secret

Only time I've seen it as practical online is to make room for an ally so he doesn't die. You've got 10. He's got 1 and about to lose it. You give him one of yours and you've got an ally who's still remotely alive.

hmmm... interesting tid bit.  Could u put a SB there, with Enforced Loyalty to prevent anyone from colonizing it?

To be honest, I don't mind scuttling for ally, but usually if I know I'll be out matched an certain I can hold off for at least 1 minute, I would suttle to prevent it from one more planet kill count to my enemies.

However, as I am aware, suttling does kill off any unbuilt buildings and not sure, but your defenses also?!

I have another solution: You scuttle a planet to make space for intergalactic hyperspace detour highway. Of course the plantet remains intact as the vogons need several Years to finish the bureaucracy...

yeah, them Vogons take forever.