Why don't the police investigate some types of crime?

they do take the reports in most matters, but due to budget matters police have to put their priorities on the major crimes and unfortunately that does put a squeeze on the simpler ones. They also understand that loss of property is serious to the person that has suffered loss. Those cases are worked, but a great deal of time is not dedicated to them. Sometimes the loss is recovered and the case solved, more likely than not it is turned over to the insurance company and loss is settled. I hope that you have insurance. And keep in mind if you do get a lead report the lead to the officer so that time permitting it can be followed up on.