I think this is probably redundant for a lot of people. I think there are some potential uses however. If I have a hotspot, I can use my ipod touch and the Wifi connection. This leaves my phone able to stay in my pocket and i don't have to worry about connecting it. It also opens BMW apps to android users, as now you can just hook up an old ipod touch. I imagine this 4G connectivity will be better because it uses the sharkfin which is outside of the car. You will also not have to worry about draining the battery on your phone.
Also, for me, I can't use the hotpot feature on my phone because I have unlimited data and Sprint won't let me.
It might not be necessary for everyone, but it is a technological improvement and will be useful for some people, so why poo-poo it?