User blog comment:Healingmantra/New attribute for supports/@comment-5035765-20161206010604/@comment-1330314-20161207214632

I'd say at this point supports might actually get less benefit than many other classes, because the lack of scaling on their abilities, and the huge focus on item-based actives, means that high uptime on their abilities is less scary than, say, a mage with the same amount of CDR. As said above, too, "prioritizing" CDR is not difficult for any class besides tanks, and does not require major tradeoffs in power like it used to, with Morellonomicon and Essence Reaver as prime examples.

In any case, none of this actually pertains to stat binding. When you bind a stat to a class of champions, you're saying that the stat is so desirable on that class, and not to anyone else, that members of that class are naturally pushed towards buying that stat, whereas others stay away from it. CDR is a desirable and widely available stat to everyone, which is why it is not bound to anyone in particular. Supports need a stat that they can make great use of, but that few other champions would ever want, and a utility-enhancing stat would be perfectly suited for them.