I’ve used Macs for about 5 years now(13in Macbook Pro, 11in Macbook Air, and now a 13in Macbook Air). There certainly are other softwares for music playback, but all of them were heavy and laggy, not to mention the cost and the not so user-friendly UI.
I always found this ironic, as iTunes lacks audiophile features that other Windows OS players(ex.foobar2000) had. There are lots of audiophiles using Macs.