Zed is making a number of points, so I don't want to sound like I'm arguing against all of them. But particularly on the matter of each... if all we were talking about were each I think Zed would have an excellent point. But wrapped up with each are all of the other fantastic enumerable methods like map/collect, select/find, inject/reduce, as well as each_cons, each.with_index, map.with_index, etc. These are where the power and expressiveness of ruby really come into play. For example:

  users.select(&:meets_some_critera?).each(&:update!)

You could totally do that in a for each loop if you wanted. But it isn't really composable. While this works for the basic update...

  for user in users do
    user.update! if user.meets_criteria?
  end

... what if you wanted to then sum up the new account balances? In the first example, you'd just chain on a couple more enumerable methods:

  users.select(&:meets_some_critera?).each(&:update!)
    .map(&:account_balance).inject(&:+)
  

With the for each construct you'd have to pass in an accumulator variable and keep track of whether to sum or not. While you certainly can do it in a for each construct, I'd argue that you'd be missing out on what makes ruby, ruby. And getting beginners in that more functional(ish) frame of mind sooner rather than later is a very good thing.

--edited a few times for formatting/clarity