Explain why theater is often considered a social event.

Though the word theatre is derived from the Greek theaomai, “to see,” the performance itself may appeal either to the ear or to the eye, as is suggested by the interchangeability of the terms spectator (which derives from words meaning “to view”) and audience (which derives from words meaning “to hear”). 
There is a widespread misconception that the art of theatre can be discussed solely in terms of the intellectual content of the script. 

Yet it is often assumed that the theatrical experience can be assimilated by reading the text of a play. While reviewers in the mainstream press may give greater credence to such elements as acting and dancing, critics in the more serious journals may be more interested in textual and thematic values. 
This is not to say that the contribution of the author to the theatrical experience is unimportant. The script of a play is the basic element of theatrical performance. In general, the truly memorable theatrical experience is one in which the various elements of performance are brought into a purposeful harmony.