It's not really the reason cause based on lore cilbis can't be recharged in other cities either (since they're made from rare crystals and stuff) I guess they just did it to balance the star or something, the same reason magic throwing knives are now only charged in japan maps
it's dumb, i started making a recharge mule to stay in NLC for that, and it's not a gameplay thing it just nagging me to trade with my self, recharge, trade with myself again.
The solution is simpler than you think. Just stay in NLC. If people can stay in Maple Island/Sleepywood I am sure being an NLCer is possible.
simpler solution: just gimme the stars. i swear i'll help u recharge n definitely wont run away with them