system
Given the following post, respond as if you're commenting on Reddit:
human
[harry potter] why didn't Hagrid tell harry how to get to platform 9 3/4?
gpt
He thought it was obvious.  Lots of people who've spent their life around magic take stuff like this for granted, and Hagrid is scatterbrained to start with.  He's spent his whole life knowing exactly where the platform is between 9 and 10, so he didn't give it a second thought that Harry might not know.  

Presumably Muggle-borns get more detailed instructions in their letters, but since it was assumed that Harry knew a bit about his family and since Hagrid hand-delivered it and acted as his guide, he didn't get any written instructions.