Why Has the Requirement of a Written Transfer to Effect

Why has the requirement of a written transfer to effect a disposition of a subsisting equitable interest caused such difficulties over the years?

A) Transferees were often simply unaware of the requirement, and made oral transactions.
B) Transactions involving equitable interests are complicated, so it was often difficult to effect a written disposition accurately.
C) Transactions involving beneficial interests are prone to fraud, so that many of the cases that came before court involved complex issues of fraudulent conduct.
D) Transferees were seeking to avoid paying tax on a written document of transfer by seeking to effect dispositions orally.