Is this a troll thread? A built-in projector would add a considerable amount of bulk for a lightbulb that generates a sufficient amount of light, optics for image enlargement, and a battery to supply a usable amount of power.
Perhaps the latest smartphone with a built in projector to be released was the Samsung Galaxy Beam 2. At this point, smartphones with built in projectors are still very much a niche product. Most people will not use the projectors because in most situations you're using a smartphone, you don't have a flat surface on which to project an image. Even then, these phones are intended to have the projectors on in a dark room.
Not saying a built-in projector is impossible, but it's not ready for prime time. In a few years, technology may have advanced far enough that their incorporation is more commonplace, but it's not mature enough for Apple to adopt. Such devices are also only found in companies that have an extensive, differentiated lineup like Samsung. It doesn't fit in with Apple's strategy to release a niche device like this.