Many people produce content and many people collaborate on such content. They have a reason to do so, they want to make their work available to the work so that select a license. Often, this content is produces as an extra to something else.
You would create a spell checker under the GPL, but it is incompatible with the GFDL, the CC-by-sa ... You would create a machine translation engine under the GPL ...
The best reason for selecting a Free or Open license for software is because you want to ensure that the freedoms will remain available to the people who receive the programs downstream. In essence it is a defensive measure using copyright law.
Facts are different from programs. You cannot copyright facts. You can copyright collections of facts. Large collections of facts are available under a Free / Open license and these are incompatible with other Free / Open licenses. This means that you either take these collections and just use them, or you get into long discussions about licenses. Either option has its issues.
When you get into discussions about licenses, you have to indicate that the license does not liberate the facts for use in another setting. People get really grumpy even upset when they are told that their favourite Open or Free license is the issue.
The worst thing happens when you are asked to cooperate on a project. A project that has obvious merits. You are asked to help out because you know the subject matter. You are asked to help and comply with their license. You are asked to collaborate for free but you are not permitted to use your own work. When you then tell these people that you do not want to collaborate because their Free / Open license is an issue, you first get stunned silence and disbelief and then you get the same old religious arguments why their license is best. To me licenses are only great if you belief in the copyright system. I believe the copyright system is evil.
In OmegaWiki, we make our community data available under a combined license, CC-by and GFDL. In this way we reach out to both the Free and the Open communities. The people that use our data downstream can pick either license or when their license is more restrictive, they can even re licence our data. Our data will remain Free / Open. People can come back to us and improve and append our data and from OmegaWiki it will be available to the people who use the data downstream.
We are happy to cooperate with anyone. We are happy to collaborate on any database of facts but we have to insist that we work in our community environment. Facts need to be liberated and be available to all. This notion I learned from the people I met in the Open Access world.