What's even odder Data seemed to have a built-in system to NOT improve himself or achieve goals. When he thinks Q is going to grant him with humanity at the end of (Deja Q?) Data is pretty quick to dismiss it. Same with when Riker -with the power of the Q, was going to give Data that gift. Data turned it down simply because he didn't want to have to "thank" Q for it. What kind of logic is that? Something in Data wanted to be as human as possible so he strived to achieve as much as possible but innately within him he DIDN'T want to be human!
That's not odd at all. In both cases, it would've been something just handed to him rather than something he achieved through his own efforts. It's perfectly understandable why he would've rejected that kind of an artificial leg up. He didn't just want to have humanity handed to him, he wanted to be worthy
of the achievement. He had a sense of inadequacy and incompleteness, and if he were just made human by some outside agency, he wouldn't feel that he deserved it, that he'd earned it. It would feel like a sham to him, a constant reminder of his inadequacy to achieve the goal on his own. So of course he rejected it.