People that want to break the laws that govern a sport or activity simply because they don’t agree with the law only end up strengthening the arguments for even more restrictive laws and can ruin it for those that are obeying the laws. Being an activist for change is more work and takes time, but it is a productive way to bring about change. It also might give you some insight as to why the laws were enacted in the first place.
I don’t know why the UK chose 25 kilometers per hour any more than I know why they drive on the left side of the road, (or why so many other countries drive on then right). I do know that when I am there that I shouldn’t take it upon myself to decide that driving on the left is not for me and just go ahead and drive on the right.
No one is restricting anyone to riding below 25 kph, (15.5 mph). They are requiring that if you want to go faster that you have to do it without assistance. In “eco” mode, my Yamaha Cross Core starts to cut out at around 17 mph, but when riding on tarmac I am typically at about 19-23 mph, and down some of our local hills, I am riding at over 40 mph. When I am accelerating from a stop or near stop, or on a hill, the assist is very welcome. IMHO, anything more would be contrary to the reason why I am on a bike instead of a car or motorcycle. I admit that 15.5 mph in the UK is a bit slow, but I also feel that people racing around unrestricted is only going to provide your government with an argument for more restrictions and even the elimination of Ebikes. Just my two cents.