Because telling everyone that they have to have religion is such a strong compulsion that people can't even resist doing it in an article supposedly aimed at programmers.

He very clearly states its not about religion and that he isn't religious. Just a poor title.

But like "spirit," "spiritual" is still really a religious word. If (hypothetically) I just happen to think that the universe operates according to normal physical principles, with no gods or magic, and that what is important is life on earth, then I am not "spiritual" and thus, according to this guy, I am a worse programmer.

This is just social pressure to conform to certain kinds of ideas. The fact that the word "spiritual" allows me to self-label as religious even if I don't belong to a large institution like the Catholic church is not very helpful if I am just not religious. And why should I have to be?