What you're referring to is more registration than licensing. You go and register the bike, the police keeps the serial number on file, and then if it gets stolen they know what the serial number and/or registration number is. If it turns up somewhere the number can be checked and it will show as being reported stolen. Really I don't see why they have laws requiring registration like that, since it's easy enough for a bike owner to write down the serial number and keep it in a safe place, then give that number to the police if the bike is stolen. But I suppose with registration if they find your bike laying out somewhere they can either call or stop by your residence and see if you know why your bike was abandoned somewhere, or if it was stolen it would be easier to get it back to you. Many departments often collect hundreds of bicycles every year to be sold at auction when no owner comes forward to claim them.