Most of Percy Jackson took place outside of Camp Half Blood, unlike Harry Potter, which takes place mostly at Hogwarts, so it’s not surprising that Hogwarts got more detail. Also, Camp Half Blood had like 50 people in it unlike Hogwarts that had hundreds, so naturally it’d be less noteworthy.
Edit: I just checked and only 6 of 22 chapters of The Lighting Thief take place at CHB.