They have an app now???
But it sounds like you mostly download stuff to your device. It doesn't sound interactive. Like I don't have to be online to flip page-to-page in the Watchtower. I have to download the whole thing first. On the other hand, maybe searching is onlne and you get shown books you can choose to download?
So the wifi is primarily for convenience. In case you forgot to pre-download your watchtower or bible study book ahead of time? And didn't have cellular data to spare?
Next thing you know, they'll have apps to track your field service. Turn it on when you start, turn it off when you're done and it automatically gets filed. Probably requiring GPS to be enabled so they can make sure you're not just sitting at home turning it on and off.