It is important for several reasons;
Firstly is saves great hassle on a day to day basis. The law is very basic, it only states a power limit and a power to weight ratio, it does not mention where the power is to be measured, or how it is to be measured. It also doesn't mention that any certificates or proof are required to say the motorbike is restricted.
The law is practically unenforceable, police usually have little idea as to the 25Kw law, how to prove that a bike is restricted or not, and are usually uncertain on what certificates are required to prove the motorbike is restricted. It is a matter of fact that there is nothing stating that there must be evidence the bike is restricted.
All this does is creates more hassle for both the rider and the police force.
Additionally is could be said that having a 25Kw restriction can be more dangerous, there have been instances where the lack of power has caused more danger because the rider in question does not have enough power to get out of a sticky situation quickly or effectively.
It is also a discriminatory law, as if you are aged 21 or over you can go straight to a 1000cc 160bhp motorbike, where as an 18 year old is limited. There is no evidence to suggest the 18 year old on a unrestricted bike is more likely to crash. So where is the point in the restriction?
Also, a 17 year old could pass their car test and go straight to a 500Bhp sports car. Whereas on a motorbike they could not do this.
In matter of fact, if a middle aged (say 40 year old) has never been on a motorbike, takes their test and goes straight on to a sports bike they could be more likely to crash than an 18 year old on a slightly slower and smaller but still full powered motorbike.
So in conclusion, is it much fairer and safer to abolish this almost totally unenforceable law, save the police countless wasted hours (allowing them to be catching the real criminals) and not appearing to be useless to the general motorbike rider population.