[marvin]

Or imagine that you're not Stephen King, but an owner or founder of a large software company. A disgruntled employee on your team downloads the source code for your entire software product (which you spent millions of dollars along with years of development work and market research creating) and sells it himself, undercutting your prices and taking all your profits. Copyright is essential for any field that involves intellectual property.

[tomjen3]

If I did that, I would be out of job and liable for loss related to loss of company secrets.

You don't need copyright law for that.