Why do players under 18 almost always reject your transfer offers but will accept them from other teams?

Always the same, I like scouting youth intakes from notable teams on the day that team gets their youth intake so I can spot wonderkids early and put them in my shortlist, whenever I can I ask the agent if the player has interest, always no no no until they're 18, or close to 18. Then at one point they're discovered by whatever european team at 16, and they arrange a transfer so he joins them the moment he turns 18, or for european wonderkids, the next transferwindow.

Just hurts to see wonderkids I've been scouting since they day they existed in the game constantly reject me and drool at the first offer from another club.