Why not just make a movie file?

Size and scope are the reasons.

For example:

A. 242 Kb JPEG image file file
B. 22 second, 584 Kb MP3 audio file.

When we put them together what do we get? Will it be an 826 Kb file? No, when you put these 2 files together, you end up with a 7.7 Mb movie file, or mpeg4 file.
This is impractical for websites with dozens of images like e-commerce pages or slideshow pages.

What is the ADA (American Disabilities Act)?

The ADA is one of America's most comprehensive pieces of civil rights legislation that prohibits discrimination and guarantees that people with disabilities have the same opportunities as everyone else to participate in the mainstream of American life -- to enjoy employment opportunities, to purchase goods and services, and to participate in State and local government programs and services.


What is a Codec?

A codec is a computer program (or a device) that encodes or decodes a digital data stream or signal. Codecs also compress data to reduce transmission bandwidth or file size.