Simply put: Failure of communication.<br />
First of all, feelings are not very relevant, it's the subject that actually causes them that needs to be addressed. A feeling is often like a "concern" which can be either valid or invalid. <br />
In a subsequent discussion, you should first explain your own view in terms that are precise and not easy to misunderstand (giving out "signs" is simply a bad way to communicate), simply because it's in your best interest that your communication partner has an easy time understanding you. Handing out the discussion topic before it takes place is a good way to enable the other to be prepared.<br />
Second, during the discussion, the goal is to bring different needs and views together, allowing both to draft an acceptable solution (or break up). Again, this should not be emotional, but focused on the topic.<br />
Whenever problems get solved and relationships improved, the feelings will go along afterwards.
Because they're "boys" and immature. And .. since they're so young, they're just not ready for that kind of interaction with the opposite sex. But .. you can also be more direct and not expect someone to read "signs".
*some* of them will get better, as you get older.
why not just say it?
wrong signs, maybe?