A lot of this is based on how modern web developers build sites. Currently, and for some time, the mantra is "mobile first", which means you design and build a website on the assumption that most of your users are on a mobile device (essentially, any non-desktop device) and you modify the layout accordingly.
This often means that many websites have way too much white space and too little information because many folks have large desktop screens, and they are seeing a site that was optimized for a phone or tablet, and little to no attention gets paid to how it looks on your gigantic monitor.
Ideally you want to design for those situations, but its a truism in a ton of web-based industries that most eyeballs on a regular basis are people using their phones or tablets. It;s most important that it looks good there, and if you have the resources to design for a gigantic screen, you design for that too. But often that doesn't happen.