Why is Shadouge more popular when Knouge makes more sense

When Rouge is around Knuckles,Knuckles gets annoyed.But when Rouge is around SHADOW,He doesn't mind.But sometimes,Shadow gets a little annoyed.
One of the main reasons could be that in the videogames the relationship between Knuckles and Rouge hardly consists on love interest, it mainly consists in rivalry. On the other hand, the relationship between Shadow and Rouge consists in something more than just friendship or partnership. Also, there is a lot of sexual tension between Shadow and Rouge (ex. Sonic Battle and Sonic Rivals) while Knuckles and Rouge don't even have that much interaction and they don't seem to be so interested in each other.