Unfortunately I think there's a misunderstanding here - it's not the monitor that decides the resolution, it's the PC.
It's a software setting, either in the OS desktop settings or within the video driver settings for your graphics card.
You could have a 50" monitor capable of massive desktop sizes, but the default for a new PC will still be 800 x 600 to start with. You can change it, of course, but if you don't you'll still have to scroll across wide web pages.
By C+ I assume you mean BikeRadar? (since C+ is no longer
)
I can't answer for BikeRadar but I chose the narrower format to make reading long forum posts easier.
Try reading several pages of CC on 100% width over a 1440 x 900 or larger desktop size and you'll soon see how a narrower width setting can be helpful.
I do offer choice though; you can chose the default narrow format, or you can go for something inbetween - once set, it sticks.
Another reason for not offering more options is simply time. There are lots of formatting tweaks I could carry out on CC, but I just don't have much free time to experiment with them. Maybe some time in the future.
Cheers,
Shaun