The answer to 'why is my supply line' is that there are several common causes for a supply line issue, including leaks, clogs, or damage to the line. Symptoms may include water dripping, low water pressure, or even flooding. Solutions can range from tightening connections to replacing the entire supply line, depending on the severity of the problem.
If the issue is a simple leak or loose connection, you may be able to fix it yourself with some basic plumbing tools and skills. However, if the problem is more complex, such as a clogged or damaged supply line, it's best to call in a professional plumber to diagnose and repair the issue properly.