Lack of right performance tools and bad product performance observability
Often times, when a performance problem is encountered, it is caused by a lack of tools needed to detect the problem in the first place- or a lack of tools to troubleshoot suspicious performance numbers. Without the correct tools, the performance issue has a chance to slip by without being noticed and then it can cause bigger problems at a later time.
Lack of sufficient control over the product is also an important factor. Many times the solution to the performance problem at a customer site can only be found by changing a few, unfortunately-hard-coded values.