* Copyright law did not exist in Shakespeare's time. The concept of copyright did not develop until the 18th century, so there was no legal framework to protect Shakespeare's ownership of his plays.
* The plays were often performed by multiple theater companies. In Shakespeare's time, it was common for plays to be performed by multiple theater companies, each of which would create its own version of the play. This made it difficult to determine who actually owned the play.
* Shakespeare often borrowed from other sources. Shakespeare's plays were often based on stories from history, mythology, or other works of literature. This made it difficult to determine who owned the original material on which the play was based.
As a result of these factors, the plays were not considered to be Shakespeare's property in his time. However, his plays are now considered to be some of the most valuable works of literature in the world, and his name is synonymous with genius.