The academic and public debates about language maintenance and language shift in the post-1994 South Africa distract attention from the more productive and important endeavour of explaining the nature of the multilingualism observed among users of African languages in urban contexts. An explanation for this phenomenon is offered here, based on evidence from a literature overview, data from a large-scale language repertoire survey conducted in 2010 in the Vaal Triangle region, as well as interview data collected from students who participated in the language repertoire survey and additional interviews with students who did not participate in the 2010 survey. The explanatory model is based on the sociolinguistic language mode of the society, the linguistic culture resulting from the language mode, a description of the motivations for language learning in this context and the resultant effects on the domains of language learning and proficiency aimed at in the different languages in the multilingual repertoires studied. The model provides an explanation for the widespread and stable multilingualism observed among the participants and it explains the observed gaps between South African multilingual language policies and the supposed lack of implementation lamented by language policy commentators.