That's actually one of my worst fears right now; not picking up on the clues and end up accidentally friend-zoning a girl. It's also one of my worst fears to pick up on clues that aren't there, take the bait and then get friend-zoned myself. You can imagine what it's like interacting with women for me. Women are terrifying.
People just don't want to be that open into admitting they have a crush on that person because they don't want to end up involved with many issues like being unable to see each other again or rumours, or anything