Why very high frequency (vhf) and ultra high frequency (uhf) radio waves are used for communications between space vehicles and ground stations?

1).  Systems at higher frequencies can carry more information
(data, pictures, channels, etc.) than at lower frequencies.

2).  The "dish" antennas used for satellite communication, both on
the ground and on the satellite, have more gain at higher frequencies
than they have at lower ones.

3).  Radio waves at frequencies lower than VHF reflect off of the
ionized layers of the atmosphere and return to Earth.  They never
get out to where the satellites are.  

4).  All of the communication spectrum (frequencies) below VHF
were already being used for other services by the time satellite
communication started (in the 1960's).