We love erpnext because the information is clear centered. For example, this modern discuss Forum is also not widescreen- Why? Because the Information for your eyes is best view when its not stretched on full screen with.
Example, odoo that uses widescreen we find very confusing for an ERP. We sit infront of an big widescreen (standard) display format, with erpnext in widescreen it feels like a movie in the first row admit, impressive first - but for reading and understanding not real productive. what do you think?
@joelios i know this idea comes up, why is there so much white space. i think also when we fill this space with information -why else should we extend it - then there is also much overload on information. keep it simple! it is also now lot of information going on, in erpnext your eyes can follow long complex lists thanks to max width.
we also build website in widescreen but this are mainly the images for presentation not the textcontainers itself. the text (erp is textbased not image based i think) is nowadays centered always limited with a max width, (admit this max width is to discuss before you plan a website.)
i think many users that are not into screendesign do not think about the readability and usability in the first place. when implementing a feature like this it should be optional to stretch to the full monitor screen.