As gnaritas pointed out, what you're running up against in that unfamiliar loop is a Smalltalk idiom that Ruby imported. My first reaction to this was, well, it's only unfamiliar, and what you call the "standard for loop" is merely a sample bias. On second thought, though, I think your original point stands. You can't just import idioms from wherever, put them all together, and shake. Or rather, you can, but what you end up with is "far more ad hoc than elegant".

What Smalltalk has that Ruby doesn't have is a simple, regular structure at its core that everything else is defined in terms of. Although it may not seem like it, that's far more than an academic point. It has enormous consequences for the programs you can write - for the programs you can think of. Most of the computing world has yet to catch up with this insight.

In the meantime, we get kitchen-sink languages that are good enough for the classes of programs that we already know how to write and are looking to make incrementally easier. I'm tempted to compare Ruby to PL/I. But that's unfair since Ruby at least was invented by a programmer who wanted to make a language he would enjoy.