2.4GHz ia good in theory, in practice tho, every technology especially the open protocols use it so there is a lot of interference. I know that because I had to lower the 2.4GHz wifi power by a lot so it doesn't cause issues with the zigbee mesh.
As for tv I would agree if TVs came with gigabit NIC, but the majority comes with 100mbps card, so if you want to stream some high quality 100+mbps content you have no other option but to use the wifi or give up the usb port for a usb ethernet nic or use a usb hub. Not pretty solitions for sure.
And then you have the robot vacuum which can only use 2.4GHz wifi for obvious reasons. And people might have IPcams which are also on wifi.