Wordpress is a non-profit organization. A CMS can be used by anyone that can write, so that makes the "impact reach" a bit bigger. A vector tool takes time to learn, so the pool of people that will be willing to do that will be smaller, so the "impact reach" is smaller. I think in order for this to work, you would need to convince developers and designers of a product like Sketch, that making a designer tool available for free is so essential for societies to prosper. I think the motivation of a lot of open source projects is that reach they can have. This is only a theory and my opinion. Curious what others have to say on this.