Why Hex Crawl?

Especially while soloing you can spend more time focusing on the "boring" parts that live groups tend to ignore - managing food and water, accurately timing your actions, counting exact distance traveled.

Hexes are a useful shorthand for distance traveled, and I always round down any leftover movement if my movement rate doesn't equal a full hex. Thus its important to have accurate maps. Hence, hex crawling solo makes you build more accurate maps.
Because of the random elements involved in hex crawling, running a solo hex crawl is a lot of fun and can lead to many unpredictable scenarios.