More About Knives

I have been given a copy of a London Local Sentencing Guideline on the 'Sale of knives and certain articles with a blade or point to persons under the age of 18 years, contrary to S141a Criminal Justice Act 1988'.
The starting points run from a low level community order for 'failing to check identity or shop policy not followed', up to 12 weeks' custody for 'deliberate sale in dangerous circumstances, e.g. heightened tension in area of shop due to gang rivalry'. Overall the range is from a low level community order to 26 weeks custody. The usual reduction for a guilty plea applies.
This all puzzles me a bit. For one thing it is not an SGC guideline, and I have no idea of its provenance, although I am sure my Clerk approves of it. The other thing is that this deals with the sale of knives to under-18s with harsh punishments for shopkeepers who do so, but just how common is this? At a guess, I have at least 30 potentially lethal knives in the kitchen, not to mention the ones in the garage and in the shed. How likely is it that a teenager will pop along to the ironmongers or to the kitchen shop to get himself tooled up, when his and every other home in the country will have more than enough knives lying about to do the job?
I have a hunch that this will prove to be just another gesture, with few if any cases coming before the courts.