Gromit - // Is this a mental health issue? No such mitigation appears to have been presented by the defence. //
This appears to be a fair rebuttal of Canary's point.
Where mental health is a factor in criminal behaviour, then it is absolutely right that it is brought into the proceedings and assessed as a contributing factor.
But if there had been a mental health aspect, then the defence would have quite rightly introduced it, and since they did not, the inference is that it was not actually a factor in the defendant's behaviour.
To address your question then, and I am absolutely not a 'punishment hardliner' - what is achieved is the application of society's laws created ad implemented to protect society from illegal behaviour, and society can see that its laws are being correctly and fairly applied which is the mark of a civilised society.