Developers work hard to come up with cool new features that will make your life easier, and if you don't update, you won't be able to take advantage of those. With Facebook, for example, recent updates brought the ability to stream live video. With YouTube's latest update, out today, it finally incorporates split screen mode on the iPad , so you can watch video while working on something else (multitasking FTW). And in iOS 9.3, there's a new "Night Shift" mode you can switch on that makes your phone screen a warmer, more sleep-friendly hue once the sun goes down.Luckily for apps, you can turn on automatic downloads so you never have to think about updating an app again — they'll update on their own (just be sure to keep "Use Cellular Data" switched off so your cell phone bill doesn't take a toll).But as for your mobile or desktop OS, you have to give the device permission, accept the updated agreement terms, and then go through with the download. Once it's done though, your device should run faster and more smoothly than before. But most importantly, it should be more secure.