It gives you total choice over what level of abstraction you want, so this is a particularly egregious use of it, being as nothing about that query is dynamic :)
You can use it purely to execute handwritten SQL queries loaded from files, or stored procedures, or any level of abstraction between raw SQL and the monstrosity you posted. The model layer is totally optional and is built cleanly on top of the query/relational layer, not inside of it.
The thing is a fucking work of art to be honest. The design shows impeccable taste, ruby's more exotic features are deployed only when really needed, everything is so clear, especially if youre used to activerecord.
BTW also the developer is super helpful and pops up everywhere to answer questions.
if you are learning sequel, stop by the irc channel and he'll probably answer your question.
EDIT: I just went to look at the github: 1821 stars, zero issues. And yes, github is the projects official bug tracker. There are 662 closed issues.
I must see if I can arrange for work to send him some money...