A question on why Serbia doesn’t recognise Kosovo’s independence

Sorry to ask a controversial question. I’m curious why Serbia’s government and many Serbians still believe that Kosovo is part of Serbia. I know that Kosovo used to be part of Serbia but the whole of the former Yugoslavia was split into several countries and Serbia doesn’t claim other territory of what used to be Yugoslavia. I’d understand if Serbia was to claim Republika Srpska as most people there are Serbs but they don’t. Serbia also allowed Montenegro to become independent and recognises their independence even though Serbia lost its entire coastline because of it.

So why does Serbia not recognise Kosovo but doesn’t claim other parts of former Yugoslavia?