The keyboard is one of the most frequently-used interfaces on any iPhone, and that’s not just because it’s useful for texting, but also because it’s the one tool you use whenever you browse the web, jot down notes or reminders, or search the App Store for your favorite apps, among other things.
While it’s certainly possible to download third party keyboards from the App Store to replace iOS’ native keyboard interface, you’d be hard pressed to find anything nearly as powerful as what can be had with a jailbreak tweak. That’s because jailbreak tweaks often let you keep Apple’s wonderful native keyboard while still enabling you to augment it in ways that Apple otherwise wouldn’t permit on a stock handset.