Because Cheeky has always kept stringently to the speed limit, never been distracted when driving, kept her hands on the ten at two position and has never broken the law.
Not drank before the age of 18.
Not had sex before the age of 16 (I didn't, I needed that makeup for a reason, ladies & gentlemen!)
Never taken £1 from mums purse to buy sweets
I'm serious, cheeky - I do know people who are, or at least appear to be, enviably moral. Regrettably, I am not one of them, and the OP also has made her mistakes.
The truth is though sitting and recriminating about what a terrible person you are is rarely productive. What is productive, whether you broke the law or just made a legal but stupid mistake, is saying 'well, ok, that happened, how can I best put this right and if I can't, how can I move on and ensure this doesn't happen in future?'
At the end of the day, I don't condone stealing but they were ink cartridges not luxury clothes or jewels - I don't know what the OP was thinking either but in fairness I think she is also 'why did I do THAT'.
So all you can do is move on. People do make mistakes, the law will punish for it but the law will also move on.