You can't talk about intel's slide show projector without talking about CPU's. Their graphics marketshare is without a doubt due to their CPU marketshare. I'm not sure what point you're trying to make regarding discrete GPU's.
Let me ask more directly:
Why are more people choosing to use only Intel Slide Show Projector© on their instead of asking OEMs or retailers some wonderful Nvidia or AMD dGPU?
Are people getting more stupid and not seeing how awful Intel graphics are and then not buying dGPUs, or is Intel Slide Show Projector© improving to the point of some people are already deciding to go without dGPU?
BTW, market share =! attach rates