Gutenberg's copy of Moby Dick is 1.2MB[0]. Which is to say the slowest benchmarked terminal could display a paltry ~53 Moby Dicks per second, while shitty gives you ~98 Moby Dicks.
I am not sure how many Moby Dicks I require per second, but it is good to have options.
Sometimes you want to dump a LOT of debug to the console but not have the console slow down that program. Or you accidentally cat a TB file?
Besides, most screen only show 60 images per second. That's not many Moby Dicks per second.
Mere 25-30 years ago I saw some very chatty Java builds run faster if the terminal window was obscured or minimized. Slow console output held back the compilers.