After doing a fairly quick random sampling and research of the Schedule 1 drugs I found that many of them were prescribed at one time or another and some of them were used as recently as the 1980's. This was just looking at maybe 5 or 6 of those listed. One I found is still used on occasion in hospital settings, and another I found is said to still be used in parts of Europe.

 

That is because at one time most of those drugs where not schedule 1. In the USA no Schedule 1 drug is legally allowed to be prescribed by FEDERAL law. The only exception to this is Pot, and that is only on a state level, it is still not allowed on a federal level. MDMA is a great example of a drug in the 70s and 80s that started off unscheduled, then became schedule 3 I believe and was prescribed for a short time, but when it became popular recreationally the government bumped it to schedule 1 therefor dissallowing it.