[amsat-bb] Orbits

[ANTHONY JAPHA]

Greetings all,
Can someone explain why the only orbits ever discussed these days--and for the past decade and more--are either very low or very high?  What really happened to the AO-7-type orbits that were prevalent in days of yore, and so useful?  Why aren't current day birds ever placed in these orbits?  Are they incompatible with today's launch vehicles or their intended orbits?

Many thanks and 73,
Tony, N2UN
LM 183