Because martial arts makes you more balanced, limber & flexible - it generally leads to LESS injury in people's lives. Not the other way around!
The great thing about martial arts is you can be at any fitness level and do great. That's because there's no rush or pressure to do anything quickly. You can learn at your own pace.
If you have a knack for it, you can speed through techniques. If it's a bit harder for you, take your time. All we care about is that you're having fun, learning and progressing, and staying safe.