In the case of traffic information, some critical targets may not show up on cockpit displays. In the case of weather graphics which can take up a lot of bits and bytes a file simply may not be able to squeeze through a too-narrow pipe er, bandwidth. Bandwidth is sometimes expressed as a function of how fast data transmissions take place sort of the way we speak of modem speeds. The higher the frequency, the more data you can transmit, but range is somewhat less and the power required to make those transmissions goes up. That s another matter.
Airplanes also have to be in a position to receive uplinked weather, too.
They have to be in the line of sight of ground-based antennas and within the coverage areas of any satellites being used for weather or any other uplinks. When it comes to coverage, satellites win big over ground antennas. From their perches in orbit, satellite signals can cover entire continents and reach airplanes at any altitude even on the ground, and even though they may use higher-frequency transmissions. The problem here is that airplanes at too low an altitude, or flying around high terrain, may not be able to receive signals from a ground antenna, in much the same fashion as they might not receive a VOR signal. To correct that problem, service providers using ground antennas have to install plenty of them in order for coverage levels to be acceptable.