Because for a given amount of physical bandwidth & power, 5G is going to be faster. 5G utilizes the available spectrum much more efficiently to give greater speeds on a given signal.
There's no way I would have been able to stream 1080p videos on TMobile's LTE 600 MHz band at that distance from the tower.
Yeah, that's one of the things that's great about the 600 MHz spectrum. While it can't penetrate mountains, it can penetrate lots of other stuff. It's the old spectrum formerly used by UHF analog TV.
Don't get me wrong, I really prefer being on their 2.5 GHz when I can get it. It's way faster, but I'll take "fast enough" over nothing.
There's no way I would have been able to stream 1080p videos on TMobile's LTE 600 MHz band at that distance from the tower.