you should care if you are a bitcoiner because crimes using bitcoins affects the reputation of bitcoin . do you like it when someone says bitcoins is a scam and a tool use by criminals ?
i heard it everywhere and it breaks my heart .
organized crime that is done by two or more people is is more serious than unorganized crime done by a single person because they can dealt a lot of damage .
There are other ways to fight criminals than tracking their expenses
if the crime happens in btc . tracking their btc transaction can help solved the crime than using methods that are not connected to btc
I hope you fully understand that crime can be connected with any currency, right? Do you think that criminals in the streets, selling drugs or weaponry, operate with Bitcoin? Bitcoin was notorious a few years ago, due to the Darknet markets, such as Silk Road, Agora, Alpha bay and many more, selling all kind of illegal items, from illegal substances to counterfeit notes.
Cryptocurrency is still used in the Darknet due to their nature of being anonymous, it's definitely an alarming issue, but I don't think there's much you can do, crime is everywhere.