That's not the problem. Rin's death was like.. ohhh. Nothing like Itachi's or Jiraiya's death.
We, the readers, know nothing about Rin. Therefore, when Obito's motivation is about Rin.. it's damn near stupid. If we knew more about Rin, then Obito's feelings would portray onto the readers.
She was his best and only friend (only friend until he was assigned to his cell)from his early childhood (ages 6 or 7). She was only one that understood him. (I made a thread about it one time you can check my threads for the argument, which talked about why obito's love is deeper than naruto's yet naruto's is more commonly accepted).
Everything makes sense, the reason the reader cannot connect is because she doesn't pertain to the main plot. We can connect with characters through naruto, but not through obito, because unlike naruto, we don't understand obito. We have never seen the story in depth threw his eyes, so it's difficult to connect seeing as there is no connection from rin to naruto.
So basically, the reason is because we don't understand obito, and cannot sympathize like we can with naruto, which is the reason we can become connected to the characters in his life but not the ones unique to obito's life. It was never explained why he loved her, or why he wanted to be hokage or anything of that sort, so his motives are not understood.