Its not that "they" don't care, its that "they" can't do a whole lot about calls outside the US and if everyone had YOUR attitude about it, they would have no reason to care.
This is another dial-back number for some IRS scammers. If you receive a threatening call from these thieves, do not call them back. They are not the IRS. They will steal your money, identity, or both. Also, don't waste your time reporting this scam number to the IRS, FBI, FCC, or FTC. They don't care.
Its not that "they" don't care, its that "they" can't do a whole lot about calls outside the US and if everyone had YOUR attitude about it, they would have no reason to care.