Apple partners with both Qualcomm and Intel for modems, and only Qualcomm offers a modem capable of 1 gigabit download speeds. Bloomberg reported Intel won't have a modem with same capability ready until after the iPhone 8 enters production.
Thus, Apple will stick with 4G LTE in its iPhone 8, even though US carriers have touted gigabit rollout in 2017. Gigabit connectivity is supposed to offer fiber-like speeds via wireless and be 50 to 100 times faster than before.
Apple doesn't like to put its trust in one supplier in case issues arise. Furthermore, Apple is in a current legal battle with Qualcomm, accusing the chip maker of withholding contractual payments it owed in retaliation for Apple's cooperation with South Korean regulatory investigators.
The FTC also accused Qualcomm of having an illegal monopoly and using anti-competitive tactics to maintain a monopoly over semiconductor supply. Apple will shy away from full trust in Qualcomm, reported Bloomberg.