The write-ups of gnomes specifically reference their use of illusion magic to hide and protect their homes, and their working with good-aligned fey to the same end.
The write-ups of dwarves specifically calls out their martial traditions and their piety.
The write-up of elves specifically calls out their martial tradition with sword and bow, and their magic tradition.
The halfling tradition...says that they are farmers that love good cheer, good food and fine comforts.
And also, what the write-up says is that halflings “avoid notice”. Fair enough, they avoid trouble in the first place, they are good at scurrying out of the way if it looks like a fight will start, they are even naturally stealthy and good at concealing themselves behind larger creatures.
Concluding that they are good at hiding their entire community IS a pretty big extrapolation from what is described, especially since gnomes who DO hide their entire community are specifically described as doing so.
So why is it that gnomes have such a better write-up than halflings?