Generally, DAPs comes in either Android or their custom proprietary OS. Many people nowadays prefer to stream music rather than downloading it onto their devices. In contrast, others don't want to rely on an internet connection and listen to their music collection offline.  There are great music apps for iPhone and Android if you belong to the latter group. Google offers various paid or free players like rocket players, black players, power amp, and shuttle music players. So it depends on your personal needs.