So the 3.5mm jack takes up too much space in a device meant to fit in your pocket. I'm not sure I agree with the decision, but I follow the reasoning. And an RJ-45 port for ethernet would have made Macbooks too thick. Yes, this is true, and I have a thunderbolt-to-ethernet adapter plugged into my Macbook at work. What possible reason could there be to eliminate a 3.5mm port on a laptop? Is it too big? Really? My laptop's screen and keyboard don't have to go completely to the edge of the case - I can deal with a small border. I can deal with a few extra cubic centimeters in the computer reserved for various ports if it means I don't have to carry about a special dongle.
While we're at it, how about asking customers how often they use the letter 'x'? Think of how much space could be saved if we just removed that one key! (Don't worry, you can still type 'ks' to get the same phonetic sound.) Now that I think of it, 'c' is redundant too - we kan get by with the letters 'k' and 's' there as well.
If it's really just about size, why not try using a 2.5mm jack instead? At least any converters wouldn't need any proprietary technology. Just because I don't use it all the time doesn't mean I don't need it.