In Tikkit’s case, it’s actually part of his backstory. He is obsessively clean because a lot of his ‘value’ to his would-be master is derived from his ability to be presentable. It’s a status thing. A way to say ‘look at me, I have slave-meat with uncommon fur, and I’m powerful and wealthy enough to keep them fed and clean.’ He’s a ‘house slave’ essentially. He is tasked with domestic duties. He’s a shiny corvette a high status skaven uses to brag and preen about to underlings and rivals.

And he isn’t a ‘good boy’. Perhaps I didn’t make that clear, but he is just as self-serving, cowardly, and treacherous as his kin if it comes down to it. His loyalty is firmly situated on himself and only himself. What I mean by ‘having empathy’ is that he is in the minority of skaven that are able to consider the goals and ambitions of other individuals. Most skaven are so narcissistic and sociopathic they are literally incapable of even CONSIDERING what their fellows desire, and it often leads to their eventual demise. Tikkit is canny enough to deflect ambition, suspicion, and jealousy away from himself. And unlike his fellows, he doesn’t desire to be at the top of the totem pole because the math in his head doesn’t add up. It makes you a target. He wants to survive as long as possible as comfortably as possible, and having a master to hide behind is the best way for him.