I prefer USB ports on the monitor, which can have a higher speed without creating problems.
Most keyboards are designed for low speed USB links, not even for USB 2.0. Having to replace the cheap cable normally used by keyboards with an expensive cable, at the great cable length that is desirable for a keyboard, would raise the cost with negligible benefits.
Many PCs have additional USB 2.0 ports for slow peripherals, i.e. mainly for keyboards, mice or graphic tablets. A keyboard with a USB hub suitable for a USB memory would need to use a USB 3 port on the PC, occupying a port that might have been better used for other peripherals, while leaving unused the slow USB ports.
Most keyboards are designed for low speed USB links, not even for USB 2.0. Having to replace the cheap cable normally used by keyboards with an expensive cable, at the great cable length that is desirable for a keyboard, would raise the cost with negligible benefits.
Many PCs have additional USB 2.0 ports for slow peripherals, i.e. mainly for keyboards, mice or graphic tablets. A keyboard with a USB hub suitable for a USB memory would need to use a USB 3 port on the PC, occupying a port that might have been better used for other peripherals, while leaving unused the slow USB ports.