There are lots of reasons you might do this.

1. Pure prior: The idea sounds stupid and you haven’t looked at the argument.
2. You’ve looked at the argument, but you think it’s wrong.
3. You looked at the argument, but then realized you don’t have the background to understand it, so you went back to your prior.
4. You looked at the argument, you do understand it, and it looks pretty good. But your prior is so strong you still reject the idea anyway.
5. You looked at the argument, you understand it, it seems strong, and on an intellectual level, it overcomes your prior. But somehow you just aren’t able to get emotionally invested in the conclusion. (Sometimes I feel this way about AI risk.)