I cannot speak for more than myself, but I ship Rarijack for many reasons. They are a classic love story, the city and country folk falling in love. Where they are so different in manners, they are also so similar in other areas. They both struggle with two sides of the little sister problem. Not paying them enough attention, and being overly protective. They both are incredibly hard workers who strive every day to make their business the best it can be. They have evolved from two people who could barely stand one another to being the best of friends with many MANY adorable moments.I don't ship Rarijack out of spite for Spike, I ship it because I think it's a relationship with enough Canon support to have legitimate fun with in fanon. I don't ship Rarity with Spike because not only the age difference, but the fact he let his feelings be known to her and she never reciprocated them. She loves Spike as a friend and like a little brother, and Spike loves Rarity as a friend. But he is only romantically interested in her because of her appearance. His affection for her would pass soon after he realizes this, and start looking for a partner who he actually likes in both body and mind. It's unfair to Spike otherwise, he deserves better.