The start of the twenty-first century witnessed the flourishing of both the biosciences (particularly genomics) and initiatives around public engagement in science, particularly in the UK and USA. STS researchers have both followed and fuelled this latter trend. Hence, it may be helpful to review the genealogy of these recent developments and of STS concern for the publics of science. This provides a way of assessing whether STS activities have been contributing to making the sciences more open and accountable to their publics. One trail returns to the institutionalisation of Public Understanding of Science (PUS) in the mid-1980s. The critique of this movement by STS scholars through reference to the deficit model (of public understanding of science) also figures here. However, less attention has been given to other modes of conceptualising science and publics, including what Cooter and Pumfrey label as the ‘diffusionist’ or ‘diffusion’ model (of scientific knowledge), which they contend entrenched traditional views of scientific knowledge and of publics as receivers of such knowledge. More recently, investigations of the making of science in diverse locations, attention to multiplicity and co-production have taken STS in new directions. Nevertheless, the legacies of both the deficit and diffusion models of science and publics continue to influence STS and its ‘regimes of truth’. Questions remain around STS researchers' persistent failure to acknowledge the diffusion model, in particular, and the consequent retrenchment of traditional views of how science works, limiting prospects for substantial public engagement and more open, democratic modes of science.