Earlier quoted context omitted.
If you don't think this crime is a big deal, then why do you think this crime would matter if it was in the public record tied to their name? These two ideas you have are not compatible.
I don't think stealing a pack of gum at 14 years old is a big deal, but many people have a huge problem understanding proportionality: To them, it's binary. You're either a criminal or not a criminal, and if this kid's record shows "shoplifter" until he dies, a significant number of people, including employers, will lump him into the "criminal" bucket for the rest of his life.
The problem that is happening in most Western countries is that criminal organizations take advantage of the fact that minors get reduced sentenced and that their criminal records are usually kept sealed (unless tried as an adult). Whether it be having them steal cars, partake in organized shoplifting operations, muggings, gang activity, drug dealing, etc...
Your reasoning for why this information shouldn't be public record seems to boil down to the fact that you don't agree with other peoples judgement of someone's past crimes. You'd like to see more forgiveness, and you don't think others will show the same forgiveness, so you want to take away all the access to information because of that. To me that seems like a view from a point of moral superiority.
I'd rather people get access to this information and be able to use their own brains to determine whether they want that person working there. If you were involved in shoplifting at 17 years old, and turn 18, I think it would be very fair for a store owner to be able to use that information to judge you when making a hiring decision. To me it doesn't make sense that you turn a magical age of 18 and suddenly your past poor decisions vanish into a void.