Firstly, it shows that your business or organisation respects and supports songwriters and composers - creators of Australian culture.
Secondly, if you use music that is protected by copyright within your business, Commonwealth legislation requires permission (a licence) from the creators of that music.
And last but not least - you benefit by using music: keeping your patrons and staff entertained, engaged and creating a better atmosphere.
Composers and music publishers generally authorise APRA AMCOS to administer their rights in Australia. Without these licences you would, for example, need to deal directly with the composers, songwriters and music publishers who own the rights in the music you wish to use.
You can get independent legal information from the Australian Copyright Council.