Reason #1 to keep writing code by hand is that you don't ever lose that connection between you and the code.

There was an excellent post here on HN that unfortunately went unnoticed. I highly recommend reading it as it exactly points out this problem: understanding.

Here is the link: https://news.ycombinator.com/item?id=50128468

Note: The post has now been flagged. Why? I have no idea but it seems incorrect.