Luffy's unintelligent, but not really as simple as I guess some people think. It's not "friend is in danger I must go." Even if his impulse is to rush it's tempered by the likes of his crew. His voyage is not about going around and having his hand forced by the opps.
Two parts here: Robin literally implies something else like the Vivi situation and Luffy declines the news. They'd just had that conversation so having it again makes no sense.
Blackbeard isn't easy to go find, you might come across him by chance or if he's set a trap. Either way, it's a very perilous effort for the sake of a Marine. Coby is a friend, but not considered family or crew. He's technically an enemy himself which is why Luffy schooled him in three out of three encounters.
He has his own people and his own path, towards Admiral, and it's complicated to interfere.
I still don't quite understand why you keep referring it as makes no sense. If you mean "Luffy will ignore/choose not to help Coby anyway, repeating his same answer twice is useless, thus makes no sense in drawing it/show it on panel", then yes, it makes no sense. Because it is repetitive and the point should get across from earlier decision about Vivi anyway. So no need to draw separate panels for 1 same plot point.
But what I'm referring to earlier (in a post you replied to) is about Coby and why Robin didn't tell Luffy about it. Of course we know it's because Oda doesn't want to deal with it now, this plot point is saved for later chapters. However it comes with a price, Robin's character.
1. Luffy is someone who cares about his friend.
2. Coby, doesn't matter his status or goal, is his friend (that's why they talk post EL despite coby being marine already)
3. Robin knows point #1
4. Robin knows Luffy and Coby are at least acquaintances that goes way back
Normally speaking, Luffy who hasn't meet Coby for 2 years, will be delighted to find info about him. Again, it doesn't matter how Luffy will react about Cobys situation, just telling Luffy news about Coby will be an act Luffy would appreciate. Because he cares about his friends.
But Robin doesn't tell him despite knowing Coby an acquaintance. It makes Robin feels like "withholding info". Oda can avoid this "detriment to Robin's character action" by making Coby's news places in another issue of newspaper that the SH doesn't get to read. But Oda doesn't. Oda had to taint Robin's character.
It also feels like she is selecting what Luffy need to know. It also feels like she is degrading Coby's standing in Luffy's mind. Oda should've made Robin said something like "there are news about vivi, blackbeard, coby, kingdom x, etc, what do you want to hear luffy?" Instead of her deciding what Luffy wants to know. In another view, if all SH reads the paper and doesn't care about Coby/not talk about him at all, it made them sounds like an apathetic people".
