SurferRosa

First, when you mention someone, if you actually want them to get a notification, you need to write out their entire name. Don't pick it from the pop-up list. It doesn't work due to a bug.

Now, to answer your question, if you play around with the gear table I linked, you'll notice that small changes in the rear cluster make a much greater gearing difference than small changes in the chainrings. Not only is it usually much easier to change your rear cluster, but those changes make a greater impact in the gearing. It's simply the way a bicycle works.