Birth records were not kept as fastidiously as they are today when Shakespeare was born, so there is no public record of his birth. His baptism is recorded in the parish church of Strarford-upon-Avon dated April 26, 1564, according to Shakespeare scholar, Terry A. Gray. The usual delay between birth and baptism was two to three days, so for lack of information to the contrary, it is widely accepted that Shakespeare's birth was on April 23, 1564.There are no records that Shakespeare even attended school.
Volumes of historical records have been lost due to age, misplacement, fire and the like, so it is amazing that we have any knowledge of his life at all. How many other writers from Shakespeare's time can you think of off the top of your head in which you know more about the writer than his name? It isn't just that we don't know much about Shakespeare; we don't know much about any London playwrights from that time period.
In her 1929 essay "A Room of One's Own," Virginia Woolf speculated that so little is known about Shakespeare because his grudges and spites and antipathies are hidden from us. His works are not held up by revelations which remind us of him. Woolf believed that Shakespeare's mind was without obstacles, so that the work could flow freely from him. He removed himself so that his works were not about himself, but about the characters and stories, which is incredibly difficult for any writer to do. Because of this gift, very little is revealed of Shakespeare's character through his writing, leaving no room for speculation.
There were no cameras in Shakespeare's day to take writers' headshots to accompany play programs. Instead, writers might have portraits drawn of themselves. There are several images which are supposed to be William Shakespeare, but none of the portraits qualify as a verified likeness of him, for no evidence exists that Shakespeare actually sat for a portrait. Even the most popular likeness of him is suspected to be false. Michael J. Cummings explains that artists might have drawn him from memory and gotten things wrong. He concludes that conclusions can be drawn based on the shared depictions of several facial features: receding hairline, mustache, etc.
On June 29, 1613, the Globe Theatre of Shakespeare's company was destroyed in a fire. The fire began on a beam of the wooden structure and quickly engulfed in flames. Records pertaining to the life of Shakespeare were likely lost in the fire, although no one will ever know for sure because they were destroyed.
People were not concerned with writer's biographies and information in the Elizabethan Age like they are today. They would only have been interested in the biography of a well established playwright, but Shakespeare didn't really gain notoriety until after his death.