One possibility is that it could leave some room for future price drops of these "F" chips, without them needing to adjust prices on their existing parts. Right now, they still have a small per-core performance advantage over AMD's offerings, but that could potentially change in a few months when AMD launches their 7nm chips. If AMD were to manage better performance all around while still maintaining lower prices, Intel might feel the need to adjust pricing to remain competitive.
And maybe Intel is simply planning to make chips without graphics in the future, and is transitioning to that model. It costs money to dedicate a big chunk of a processor to graphics hardware, after all, and when a system has a dedicated graphics card, it might not be needed.
It's also worth keeping in mind that Intel is making a big push to get into graphics hardware. Perhaps they intend to separate the CPU and GPU portions of a processor in the future, allowing them to include multiple tiers of graphics capability built into the CPU, without having to disable hardware for the lower-end parts.