This is a very US centric way of looking at this. Currently sitting in a packed subway carriage in Busan, South Korea. There are carrier WIFI APs installed in every carriage. Their network is literally built to offload people onto wifi where possible, I presume to reduce congestion on not much or very directional spectrum in the tunnels. In this case, it makes perfect sense to push people onto their wifi. Not connecting to your own networks preferentially is a pita though. Seems like a really neat solution imo