There’s a fantastic article on the LSE Impact Blog which addresses this often cited yet rarely substantiated claim:
Many academic articles are never cited, although I could not find any study with a result as high as 90%. Non-citation rates vary enormously by field. “Only” 12% of medicine articles are not cited, compared to about 82% (!) for the humanities. It’s 27% for natural sciences and 32% for social sciences (cite). For everything except humanities, those numbers are far from 90% but they are still high: One third of social science articles go uncited! Ten points for academia’s critics. Before we slash humanities departments, though, remember that much of their most prestigious research is published in books. On the other hand, at least in literature, many books are rarely cited too.
It sources and refutes the original 90% claim while also exploring some of the wider issues involved. An interesting question occurred to me: why has that 90% claim circulated so readily despite it being an over-estimation for the humanities and emphatically wrong for other disciplines? It is an ‘urban legend’ as the author puts it in the blog post. It appears to confirm a perhaps unspoken fear (“no one cares about what I write”) or a self-aggrandising prejudice (“I get cited a lot but other people’s work is crap”) and this affectively imbued confirmation bias keeps the claim circulating.