Autonomous robotic in-space assembly (ARISA) offers a step-change in tasks currently completed by risky, slow, and expensive spacewalking astronauts- e.g., Hubble Space Telescope servicing missions. The James Webb Telescope (~1 million km from Earth) cannot be repaired even by tele-operated robots due to communication delays, highlighting why autonomous robots matter at further/higher orbits. Over longer time-horizons, ARISA capabilities would enable assembling/maintaining: - larger-than-James-Webb space telescopes that enable new scientific discoveries but need ARISA as these telescopes cannot fit monolithically in current rockets; - large sunshades (assembled between Sun-Earth) for space-based climate cooling by reducing solar radiation reaching Earth; and - labs for in-orbit vaccine manufacturing, fabrication plants/fabs with improved semiconductor manufacturing capabilities, and habitats for space tourism - each offers a pathway to new and sustainable commercial opportunities in space. These larger space structures matter for science and society but, clearly, realising them in environments too harsh for prolonged human exposure requires ARISA technologies. Focusing on ARISA developments today enables tackling grander challenges tomorrow.