Not explicitly mentioned here, but worth bringing up: Text width should always be constrained to a maximum width to optimize for human reading. Every book ever printed has text with set within the same range for a reason. Full width text guarantees most users will have a poor reading experience.
I don't like that. I can adjust the full text width by adjusting my window but if have a big wide screen and you limit it, then I'm wasting a lot of what I can see. Give me customization, not "alleged optimization" that turns out not to be so
Also, don't ask users to resize their browsers to accomodate for a site's poor UX. That's called "blaming the user."