I agree with what you're doing, but I do think you're entirely wrong on this point. That's exactly one of the reasons why the police exists.

Crime (including theft of expensive equipment) should be prosecuted. It does more harm to society and the perpetrator if you let it go. If people start to think their are no consequences for stealing laptops, there will be more stolen, then more serious crime can follow.

One thing this guy has going for him is that he did return the laptop to you. I think he deserves a little credit for that.

In the sense that 'the police don't have the resources to track down small items lifted in public places by unknown persons, and there are victims of greater crimes to tend to' you are perhaps right, but I think that all changes when you actually supply the name and address of the offender and incontrovertible proof that he's guilty.

Although if you did give them that information and they still couldn't pursue it, there's not much else you can do (except, of course, bang your head against the wall in frustration).