The simple answer is because customer service is our #1 priority. We prefer not to repair large cracks over 3 inches because they are more visible after repair, take more time/money, have higher failure rates during and after the repair because of sensitivity (but still have huge success rates). Nevertheless, we have the knowledge and tools to stop a crack and truth be told if you want, we will give it a try but will not guarantee it for life. Call us for more info.