Think for a moment about how big of an impact 4g had, and 3g before it. As others mentioned above about the law that states that any new computing resource will eventually get filled, there are plenty of areas where this is worthwhile.

The biggest first off would likely be the end of wifi as we know it, so in turn, an increasing number of IoT devices for the home/workplace/elsewhere would be built without the need for complicated wifi setup, and all syncing between devices would likely be done using a cellular setup. "Cable" would likely completely go away, where companies like Verizon realize they can deliver all TV over their 5g network. The constraints relating to numbers of devices on a wifi router will be backgrounded, ect.

Another key piece is that there will be far more nodes in a 5g deployment, so you could do better triangulation for GPS. It will have lower latency so even tighter real time applications can be done over the internet. This list can go on and on.