Nobody keeps you from publishing your software under whatever license (or none at all, which I wouldn't recommend for legal reasons). Not even Mr. Stallman. He does not say that you must impose restrictions. For one-man-projects, writing code and throwing it out of the window upon the unwashed masses of the internet is probably not so much of a problem. (As long as you can live with the idea that somebody adds 2 tiny, but crucial missing bits that you have overlooked, sells the software under a proprietary license and makes a fortune from your work without you even knowing, let alone get your share.)

However, even with your own project that doesn't include other people's contributions, you could end up in nasty situations if somebody else builds upon your code. As I said, I studied law and I know how strange things can get. (Like: Depending on the circumstances, a company that used your code for commercial purposes can drag you to court and try to make you stop publishing it, change its name or whatever.) Protecting the freedom of the code prevents such things.

GPL/LGPL are more important, though, with bigger projects. Whenever a group of developers (or companies) work together like they do, for example, on the kernel, they'll most likely want to keep each other from taking their collective work and run away with it. Both licenses turned out to be remarkably smart when it cames to balance the interests of all parties involved. The rise of what you call Linux (be it on servers, desktops, phones or in embedded devices) would never have been possible hadn't the license forced commercial vendors to share back all the improvements and changes they made for their respective use cases. Also, you mustn't forget that before the GPL, there were more or less permissive licenses. I remember times when each software project had its own. It was impossible then to compile a set of tools without breaking some of the licenses involved. The clever design of the GNU makes things a lot easier here.