Archive file attribute is generally set when a file or folder is created or modified. The purpose of archive attribute initially was to make back-up operations easier and back-ups themselves smaller by indicating new or modified files to back-up program which only stores files and folders with archive attribute and afterwards clears archive attribute of files that are backed-up. Then, in the next back-up procedure, files without archive attribute are not included in the back-up archive.
Generally archive attribute does not influence behavior of most of the programs and modern back-up software. However if you use an older back-up program or another software which is sensitive to archive attribute either in single user or shared environment, you might need to regard this attribute as essential.