Epic fail

I don't nick bikes but i have nicked other things in the past and "will i get caught" was always in my mind.
You might not directly think "if i get caught, il get such and such a fine and so many hours of community service" or whatever but you think about getting caught.
You weigh up the danger of getting caught with how much you want what your stealing and the penalty if you do get caught factors into that decision.
...
If the escalation of punishment for these theft's had no effect on people then all those that help themselves to grapes wouldn't think twice about helping themselves to bottles of whiskey.
Or TVs.
Or bikes.

Yes, fear of the criminal penalties is what stops some people from stealing, and yes, harsher penalties would stop a few more but that's still only some people. Others work in many different ways.

Fear of a sense of guilt stops me from stealing grapes even if i know i won't get caught (most of the time anyway). That gets backed up with fear of loss of respect from others, as well as fear of the potential punishments. I have hopes for my future, and value my current status.

If your main motive is sustaining the substance abuse you don't care about the means, you don't care about the consequences. You go back to jail for the twentieth time and if you didn't go through a rehab you will be back for more.

If you don't value yourself or your future, even the harshest of punishments won't deter you. Some might justify punishing such people as 'getting rid of vermin', but to others, this is 'pointless cruelty to people who might have been reached in other ways'.

You can crank up the punishments as far as you like and there will still be some people you will never reach. At the same time you will be destroying people who could have reformed, and if the system is too cruel then people will hate it ever more, and those who live by principles will start to fight it and try to undermine it.

Punishment and its deterrent effect will always be needed, will never be a complete solution, and work best when the level of punishment is fair and proportionate.

Punishment levels are (very roughly) right already. Only small improvements will come from tweaking them. Much more can be gained by giving everyone a real stake in our common future; we could do a lot more of that and it would be almost all to the good.