AGPL allows you to satisfy the free software people (and the free-as-in-beer people) and correspondingly win market share and get code contributions etc., but it also scares a lot of large corporations (whether or not it should). And if their in-house bureaucrats won't let them license code under the AGPL but they still want to use it then it leaves them to pay you for the other license. Meanwhile the bureaucratic corporations are the ones with the resources to pay you anyway.