Back in the 20th century, before electric bikes, when I was but a wee lad the neighborhood Karens screeched until the local PD dropped one of those mobile "your speed is" trailers onto my street for about a month.
It turns out 12yo me could go 29mph on a mountain bike.
30 is too low IMO. Make it 35 or something. 25 is a joke.
I picked 30mph because that's the current threshold for what is considered a motorcycle in the state of Washington. Until recently, e-bikes were exempt from this because the old law was made back when e-bikes were rare and couldn't go much faster than regular bicycles.
I've gone >50mph on a bicycle, 40mph on level ground. Yes it's possible, but it requires significant effort and you can't accelerate as quickly as an e-bike. That's why I said, "and has a motor". Heck, a fast runner can endanger people on the sidewalk. When I'm running, I often slow down in crowded areas so that if someone does randomly veer into my path, I'll have time to avoid them.
If lots of people (who I assume are very fit) were riding bicycles dangerously, maybe the legislature would make some laws about that. But until it becomes a problem, there's really no need.
I like going fast as much as the next guy, but lets be real, the safety profile of someone pedaling 30 mph is not the same as someone pressing a button to go 30 mph.
https://www.reddit.com/r/bicycling/comments/1tu6v9d/scooter_...
When you're pedaling at 30 mph, you're much more likely to be engaged, paying attention, and under ideal conditions. Folks who cruise at 30 at the press of a button, tend to actually do so consistently. Anyone who rides on a bike path anywhere today can obviously observe the differences in behavior.