@Duncical
It's the website designers to set the size of the website, unfortunately given most users are currently running on 4:3 monitors (1600x1200, 1280x1024 etc) monitors, then most websites are designed to look properly on them, and therefore wasted space on widescreen 16:9 (1366x768, 1920x1080 etc)
So, long story short, until most users have 16:9 users then the website will cater to the majority of users which is 4:3. I mean, can you imagine having a 4:3 monitor and having to either missing out on the words on either side of the screen, or pull the zoom back, and then having tiny font?..