Seems like an obvious question, right? Because they're more streamlined that way, duhhhhhh. Well, yeah, that's partly true. But as it turns out, there's a lot more to it than that.
Luckily, the good folks who make the videos for YouTube's Real Engineering channel have us covered with the skinny on why things are swept back. Their animators took a deep dive into the history of aeronautics, tracing the wing's history all the way to classic planes like the WWII-era Lockheed P-38 Lightning in order to explain why modern wings look the way they do. Do you know what a critical Mach number is? Are you familiar with why the Bell X-1, the first supersonic plane, looks the way it does? Do you know about spanwise flow? By the time you're done watching this, you'll know all that and more.
In fact, this video manages to pull off a rare feat that very few science videos do: It's entertaining, informative, and easy to understand, all at the same time. So pour yourself a fresh cup of coffee and take a few minutes to watch the short clip, below. And if your boss isn't paying attention, check out some of Real Engineering's other awesome, aviation-themed videos after that.