Redis hashes are good for storing more complex data, like you suggest in your question. I use them for exactly that – to store objects with multiple attributes that need to be cached (specifically, inventory data for a particular product on an e-commerce site). Sure, I could use a concatenated string – but that adds unneeded complexity to my client code, and updating an individual field is not possible.
You may be right – the tutorials may simply be from before Hashes were introduced. They were clearly designed for storing Object representations: http://oldblog.antirez.com/post/redis-weekly-update-1.html
I suppose one concern would be the number of commands Redis must service when a new item is inserted (n number of commands, where n is the number of fields in the Hash) when compared to a simple String SET command. I haven’t found this to be a problem yet on a service which hits Redis about 1 million times per day. Using the right data structure to me is more important than a negligible performance impact.
(Also, please see my comment regarding Redis Sets vs. Redis Strings – I think your question is referring to Strings but correct me if I’m wrong!)