There are several factors that can cause power steering seals to fail, including:

1. Age and wear: Over time, the power steering seal can become worn and brittle, leading to cracks and leaks.

2. Heat: High temperatures can cause the power steering seal to expand and contract, leading to wear and eventually failure.

3. Contamination: Dirt, debris, and other contaminants can damage the power steering seal, causing it to leak.

4. Overuse: If you frequently make sharp turns or use the power steering at high speeds, you can put additional stress on the power steering seal, leading to failure.

5. System pressure: The power steering system operates under high pressure, which can cause the seal to wear out more quickly or even burst if there is a problem with the system.

6. Improper installation: If the power steering seal is not installed correctly, it can cause leaks and eventual failure.

It's important to have your power steering system inspected regularly and have any leaks or other issues repaired as soon as they are detected to prevent further damage and extend the life of the system.