For my open source libraries, I use the Unlicense, because I want to minimize licensing friction. But if I'm distributing (say) a complete end-user application that represents programmer-years of work, I'm likely to use the GPL, because I may not want somebody to fork it and make it proprietary. It's my code and my decision.
If you want to use my GPLed code in your proprietary product, you can find my email address and pay my company an appropriate license fee. And if you think this is somehow unfair, my wisest course of action is probably to avoid doing any business with you: You're raising all kinds of "horrible customer" warning flags.