Sustainability is becoming an increasingly urgent concern in technology research, yet its meaning and application within Human-Robot Interaction (HRI) remain unclear. We examined how sustainability is currently understood within the HRI community through i) a survey among HRI researchers and ii) a “speculative futures” workshop held at the HRI 2025 conference. We compare the results of our analysis to the widely adopted three-pillar model of sustainability (delineating environmental, social, and economic aspects) and contrast it to alternative frameworks that critique this categorisation. Our findings show strong—but unacknowledged—engagement with social and environmental sustainability within the HRI community. We highlight common ground, lack of shared understanding, and areas of improvement across the community, and suggest practical steps for integrating sustainability into HRI research. We formulate aspects that should be included in a definition of sustainability that is specific to HRI.