1) characters that people care about 2) a lack of satisfying emotional resolution (esp. in the context of a romantic relationship).
Your books qualify for the first, but not for the second.
YA books attract a lot of it because of their big readership among the main demographics, the fact that their emotional arcs tend to be tied off clumsily, and because fanfiction writers will prefer to add complexity to simplistic works, instead of vice versa.
1) characters that people care about
2) a lack of satisfying emotional resolution (esp. in the context of a romantic relationship).
Your books qualify for the first, but not for the second.
YA books attract a lot of it because of their big readership among the main demographics, the fact that their emotional arcs tend to be tied off clumsily, and because fanfiction writers will prefer to add complexity to simplistic works, instead of vice versa.