When I had a 13" MacBook Pro and had to work from home, I connected my laptop to my 23" HP Monitor.
However I've since ditched it for a Late 2013 15" Specc'ed out MBPr and also ditched the monitor too.
I ditched it first because my office is turning into a Nursery with a baby on the way but also because I didn't need it as much with the 15".
I should also say tho, I only used my 13" MBP with a monitor in closed mode with the TwelveSouth BookArc laptop stand. I hate 2 monitors.
Now I just work like the below:Image
That's a great setup. This is a good example of why someone would not need an external monitor. I actually had a 15 inch with the same setup but returned it because it was creaking.