Dual licensing is a common reason to GPL your code: Letting people have and use the source under restricted terms, and paying for an enterprise license otherwise.
If Google can steal the code from the GPL version and then just not obey the license or pay for an enterprise license, dual licensing is dead and no business will open source their code under a dual licensing model.
Google did not steal code. Dual licensing is not a reason but a practice. Unlicensed use of code is still unlicensed and punishable by the terms of the license. Dual licensing still exists and will continue existing.
