But it makes the trailers significantly more expensive and the shipping cost more variable because the amount contributed by the trailer will be extremely varia

But it makes the trailers significantly more expensive and the shipping cost more variable because the amount contributed by the trailer will be extremely variable. On top of that to cut down on cost you'd want the inverters to be on the tractor instead of the trailer but now you have truckers working around and having to plug and unplug live HV DC connectors as they connect and disconnect. Plus now the trailers are a hazard to worry about when they're just sitting around because there's all those solar cells creating big DC volatages just waiting for a circuit to be made.