I don't think I ever did anything as bad as described here, but certainly I've seen unethical practices in proprietary software development, and that direct experience was one of the factors which led me to FOSS. Ultimately it all comes back to the C word. Capitalism.

"The more software continues to take over every aspect of our lives, the more important it will be for us to take a stand and ensure that our ethics are ever-present in our code."

https://medium.freecodecamp.com/the-code-im-still-ashamed-of-e4c021dff55e#.z0vu51pp5