Plastics have actually experienced a pretty significant shortage this year, with resins and other components being hard to source[1]. Polaris, for example, would build their entire vehicle except the seats, then build and attach them once the plastic resin for the foam became available[2].

1) https://www.ntotank.com/blog/resin-material-market-shortages... 2) https://www.wsj.com/articles/supply-chain-bottlenecks-drive-...