A lack of time to implement it/management changing priorities... again.
I would love to and I had thought that I had convinced management why we needed to (Nothing fancy, just ssl on parts of our web page). Then something blew up. Then something else blew up... and it just wasn't that important to management any more.
Understanding the business, understanding what the code needs to accomplish and being able to communicate with the users can be just as valuable as coding experience. This does depend on the company. Highlight these areas. It will tend to look you look a bit more than a manager than a programmer, but you will get your foot in the door.