Why do psychologists have to disclose dangerous clients but lawyers do not?

When seeing a psychologist (at least in Canada where I live) we are bound by privacy law meaning that everything stays between the professional and us. However, there is an exception if the psychologist or psychiatrist deems we are a danger to ourselves or to others.

But lawyers on the other hand, can defend serial killers and rapists, make up intricate lies and use legal loopholes to get their clients ourt of jail. I get that everybody needs a fair trial and human rights and everything, but if the lawyer knows their client is guilty (which often they do), isn't this their moral responsibility to prevent more harm?

If their client is deemed not guilty thanks to their lawyer gimmicks, and then they commit another crime afterwards, shouldn't the lawyer be considered an accessory to that crime as well for failing to protect society?

I just don't get it ...