Because the Americans don't take road safety seriously.
Most recent article on that topic
The Deadly Myth That Human Error Causes Most Car Crashes
David Zipper in The Atlantic wrote:In 2015, the National Highway Traffic Safety Administration, a branch of the U.S. Department of Transportation, published a two-page memo declaring that “the critical reason, which is the last event in the crash causal chain, was assigned to the driver in 94% of the crashes.” The memo, which was based on the NHTSA’s own analysis of crashes, then offered a key caveat: “Although the critical reason is an important part of the description of events leading up to the crash, it is not intended to be interpreted as the cause of the crash.”
And the logical link to higher ebike speeds is.... what, exactly?
Short answer: 25kph. We've been through this before.
Move to WA and get an R-N scooter. (Slowly we're bringing the speed limit down as you suggest)