Answer to Question 1
Mean time between failures is a measurement of error occurrences that can be tracked over time to indicate the quality of a system.
Answer to Question 2
One key issue is that many systems professionals don't want to perform maintenance because they feel that it is more exciting to build something new than change an existing system. Also, organizations have historically provided greater rewards and job opportunities to those performing new development, thus making people shy away from maintenance-type careers.