You must be referring to the constrained width of the page, you can change that in the preferences if you really prefer having the text cover your whole screen.
There's a reason we have a character limit per line when writing code - it's much easier to read and understand short chunks of vertical text. Personally, I find it far more comfortable reading text which doesn't go above 600-900px in width and this has been a well known UX/UI guideline for the last 10 years. Having your eyes go from the far left to the far right of your screen is also very straining on any >21" screen.
