I really don't get why people don't just declare their work public domain.
Well there's one very good objective reason not to: it's not clear if you legally can in all jurisdictions. It's not clear that you can just relinquish all IP rights to something. This means that the user of the IP can't be completely sure what they are and are not allowed to do with it, and they may be less inclined to use it than they would a BSD style license where they know what they can't do.
Some public domain desgnations, like CC0, partially get around this problem by including a clause that says that if they can't relinquish all rights, then they'll relinquish as much as is legally possible. This helps, but doesn't completely get around the uncertainty.
But mostly I think they are really concerned about this
Please don't be so quick to pass judgement. First, there are plenty of people who use the GPL to maximize the amount of software that is free, for whom "jealous control" is a secondary objective or completely irrelevant.
Second, there's nothing wrong with what you label "jealous control". If someone is made uneasy by the idea of someone taking their code and "stealing" from them, but they still want to embrace their users' freedoms, and they use the GPL, more power to them.
The only way that the GPL restricts my licensees is by requiring them to not use the fruits of my labor to restrict other people's freedoms. I don't want to be involved in infringing on people's rights like that.
Well there's one very good objective reason not to: it's not clear if you legally can in all jurisdictions. It's not clear that you can just relinquish all IP rights to something. This means that the user of the IP can't be completely sure what they are and are not allowed to do with it, and they may be less inclined to use it than they would a BSD style license where they know what they can't do.
Some public domain desgnations, like CC0, partially get around this problem by including a clause that says that if they can't relinquish all rights, then they'll relinquish as much as is legally possible. This helps, but doesn't completely get around the uncertainty.
But mostly I think they are really concerned about this
Please don't be so quick to pass judgement. First, there are plenty of people who use the GPL to maximize the amount of software that is free, for whom "jealous control" is a secondary objective or completely irrelevant.
Second, there's nothing wrong with what you label "jealous control". If someone is made uneasy by the idea of someone taking their code and "stealing" from them, but they still want to embrace their users' freedoms, and they use the GPL, more power to them.
The only way that the GPL restricts my licensees is by requiring them to not use the fruits of my labor to restrict other people's freedoms. I don't want to be involved in infringing on people's rights like that.