In satellite communications, it all comes down to the link equation. For mm-wave frequencies, there is a higher attenuation due to free-space path loss and more importantly from rain/weather effects. The probability of link establishment is an important factor, with typically high requirements for probability. The system designers balance the need for higher power amplifiers in the bands with the higher data rates that can be achieved along with the probability of link establishment.
One technique to improve things is to use station/receiver diversity. In the case where weather is the limiting factor, stations would need to be miles apart, depending on the geography of the receiving station. In some geographies, mmWave frequencies are not appropriate due to the high probability of rain.
Other factors such as antenna design and directivity can increase the link margin as well as transmitter power and receiver noise figure to increase the signal to noise ratio.
