I've felt that lack of curiosity a fair amount over the past 5-10 years. I suspect the biggest change that reduced my curiosity was becoming financially secure. Or maybe some other changes which made me feel more secure.

I doubt that I ever sought knowledge for the sake of knowledge, even when it felt like I was doing that. It seems more plausible that I had hidden motives such as the desire to impress people with the breadth or sophistication of my knowledge.

LessWrong attitudes toward politics may have reduced some aspects of my curiosity by making it clear that my curiosity in many areas had been motivated by a desire to signal tribal membership. That hasn't enabled me to redirect curiosity toward more productive areas, but I'm probably better off without those aspects of curiosity.