Because Apple didn't put that sort of functionality into iPhone OS.
If I'd known you wanted to see the info of photos on a computer, I'd have answered the question that way. You posted this in the iPhone section of the forum, and anyone with reading comprehension skills above that of a retarded ape would have answered the question as such.
I think the only idiot here is the guy who:
1. Doesn't know how to view info for photos on his/her computer.
2. Doesn't know how to use Google to figure out how to view photos on his/her computer.
3. Can't write a question to save his/her life.
Good day, sir.