You should read about transfer pricing. In many cases it is entirely possible to assign where a large firm's income is made for tax purposes by internally transferring intellectual property.

On the point of why would tech companies want to do this instead of helping the community, I argue it may actually help California. Instead of doing the responsible thing and moving the firm to somewhere with a lower state corporate tax rate, the firm can simply avoid taxes. This keeps employees in the area contributing to state income and property taxes. In a world or multinationals, I am not certain corporate income taxes make sense.