[qsi]

Cause in this context specifically refers to the employee having done something wrong or illegal and means the employee is guilty of misconduct.

[rsanek]

It is very rare for someone that is fired to be "guilty of misconduct," unless you consider poor performance misconduct.

[acatnamedjoe]

In Britain we have quite strong employment laws and a bit less of a ruthless corporate culture, so in many sectors it's fairly uncommon for people to be terminated for poor performance, so I suspect "misconduct" is a higher percentage of overall firings here.