[berkes]

It indeed is convention in Rails. A bad convention IMO.

But it is enabled by Ruby, as you state, by how flexible Ruby is. It may seem a nice touch that Ruby hands you the freedom to choose to e.g. omit brackets. But I think this is a bad freedom. As Rails shows, its a freedom that leads to, IMO, harder to read, and harder to reason about code.

With any language design, the limitations as well as its features, is what make the language. Limitations are an important feature of a language, IMO.