One of the key elements to the success of Ethernet is the concept of packet data transmission, where data, images, and even sound files are divided and reformatted into small units, transmitted over the network, and reassembled for use by the receiving computer.
It is certainly possible to transmit a file in a complete stream from start to end from one computer to another. This type of transmission is often used when a system only transmits in one direction, from one device to another. Think about a typical analog CCTV setup, where one camera is connected to a single monitor. The camera sends its images in one uninterrupted stream, and the pictures are displayed on the monitor.