This sounds very similar to "Why would anyone need more than 640K?"
It's not just about speed, a 5G network supports a greater density of devices compared to a 4G one. 4G can support about 4,000 devices per square kilometer, whereas 5G will support around one million.
5G will be able to connect the plethora of next gen IOT devices coming to a store near You!
Just imagine smart shopping carts that will finally enable the homeless to have connected homes too! How about smart protestor signs that will automatically change to display what ever SJW message the technocracy wants to get out in real time. There are so many wonderful things that "Harder, Better Faster" connectivity will bring us all...Queue Daft Punk background music!!