I for example use at night as my "laptop" a cheap tablet with keyboard, it is 800px wide.
Also 980px also will suck for people with VEEEERY WIIIIDE monitors.
Or apple retina (that has absurd resolution, thus resulting in their site becoming very small and unreadable).
Websites on a HiDPI display are effectively pixel doubled, the viewing side is the same. The same happens with the iPhone 4 and later.
their focus on such an overwhelming majority of users makes a ton of sense from a business perspective.
(sidenote: does anyone with a VEEEERY WIIIIDE monitor maximize windows?)
Yes. I don't know why though.