Why do people use 2 monitors

[keemhemans]

Why do people use 2 monitors for gaming and streaming and do they need a keyboard and why

 

[little_me]

two monitors so that they can:
See what they stream and game at same time, also see what stream watchers are talking about.
While you could use bigger 4k screen and play game windowed, using rest of space for stream monitoring and other things, it is usually easier to just use two.
And yes, usually doing things that involve typing, needs keyboard.