Here's why it's likely:
* Common speed: 60 mph is a common speed limit on many roads, making it a recognizable benchmark for speed.
* "Full speed" analogy: People often associate the maximum speed limit with "full speed" or "as fast as you can go," making "go like 60" a shorthand way to describe this feeling.
* Slang usage: Slang often borrows from everyday life and uses metaphors or comparisons to express ideas.
While there's no definitive origin for the phrase, its connection to speed limits and the concept of moving quickly makes it a fitting and widely understood expression.