Why is c++ used by banks and investment banks for high frequency systems, if c++ implementation won't work more than one processor/core?

[Damian]

Hi everyone, I'd like to ask you a question about a particular case, I'd like to know why is c++ used by banks and investment banks for high frequency systems, if c++ implementation won't work more than one processor/core? Thank you very much for informing me as soon as possible, thank you in advance.