Why does the chicken cross the road?
If you were the chicken, you would likely know. Otherwise, it’s all speculation. People are motivated by very different things. Because you can only think of two motivating factors does not limit the possibilities to those. In fact, the possible motivations are limitless and need not be confined to what others may think are rational either.
Often hackers hack to because it’s challenging. Just getting into a system can be the objective. Maybe that’s what you mean by thrills but it’s really more like self-testing one’s abilities.
To be useful, critical thinking requires a logical approach. Skepticism is frequently warranted but speculation is rarely based in logic.