The similarities and differences between how Katara and Sokka are written never fail to amaze me, i already made a couple posts about it but i have more.
The way they both make reckless decisions based on emotion except Katara is prone to doing it when she wants to help anybody, even people she doesn't know (that village in the painted lady ep, following Haru and wanting to save all the earthbenders etc.)
But whenever Sokka does something stupid it's usually to save someone he cares about personally (going to the boiling rock without a plan to save his dad, attacking Azula when she mentioned Suki etc.)
The perfect example of this is in the painted lady when they have that argument and Katara says "I will never turn my back on people who need me" and Sokka decides he is going with her saying "You need me and i will never turn my back on you".
He didn't agree with her intention, the only reason he went is because he knew there is no talking her out of it and while he could turn away from the village, he couldn't turn away from Katara.
That being said it's not like Sokka doesn't want to help people he doesn't know, it's just that he is strategic about it and when he realizes that they can't do much to help, he knows that the logical thing is to leave before they get into trouble. His will to help people isn't strong enough to make him reckless and have him rushing in without a plan unlike Katara who is willing to risk everything to help even when it seems impossible.
But he is very reckless when it comes to people he loves and he would risk anything to protect them.
And that's why he always ends up joining Katara and Aang in their missions even while complaining about how reckless they are being, because even if he thinks it's a dumb idea he doesn't want them to do it alone.
