actually, if all speed limits were abolished and there was a "reckless driving" penalty (as well as much better driver training) I bet it would work OK.

They actually tried this once. Not much changed.

The slow speed limit is bad, even beyond simply being annoying. It would be expensive, or impossible to truck perishable food across large distances. For example, to bring oranges from Florida to where you live would take 10 times as long.

On the other hand abolishing speed limits would make driving very scary.

It would be almost impossible for a person to stay afloat in a vat of rubbing alcohol. You wouldn't die from fumes, you'd die from drowning