Why? Hackers operate in the digital domain and supposedly, the digital domain is impossible to secure.
If the hackers operate on the dark web using a VPN, it’s basically impossible to trace them.
If the hackers seek ransom, using bitcoin they can launder the money making it impossible to track.
The Cyber Domain for companies and government is impossible to 100% secure, someone or some group of people on the inside have Admin or Super User status, if one of those people goes bad, they have the ability to hack anything inside that organization.
Think of Edward Snowden, think of the NSA who had 50 terabytes of information stolen in a hack, the software stolen had all the secret tools that the NSA uses to hack other countries, those tools were released on the Dark Web and have been used against organizations inside the USA.
https://www.idstrong.com/sentinel/the-nsa-hack-what-happened-to-nsa/
If the NSA isn’t secure no one is.