Lex Friedman does not directly address why he prefers the long format for podcasts in the provided excerpts. However, there are various insights into the structure and approach of his podcast that might imply reasons why the long format is valuable to him.

1. Learning from Experts:
- Lex mentions the importance of learning intensely from world experts, not just their content but their way of being: "to look in to some of these world experts in a structured context, really intensely learn from them, not just the content, but the way of being" (00:02:34 - 00:02:41).
- This suggests that the long format allows for a deeper dive into the thoughts and behaviors of his guests, which can be more effectively captured in an extended conversation.

2. Extensive Conversations:
- Lex and Stephen Wolfram's conversation is noted to have lasted past midnight and covered four and a half hours: "We went past midnight, we only did four and a half hours. I mean, we could probably go for four more" (04:19:02 - 04:19:07).
- This indicates that Lex values thorough and comprehensive discussions, which are facilitated by a longer format.

3. Depth of Topics:
- The podcast addresses complex subjects like the computational nature of reality and large language models (00:00:18 - 00:00:29), which likely require more time to explore in detail.

While the excerpts do not provide a direct statement on Lex's preference for the long format, the emphasis on deep learning from experts, extensive conversation times, and the need for thorough exploration of complex topics all imply that the long format is preferred to allow for these in-depth discussions.