Unless you are very well connected, the chances of someone aged 19/20 being hired is not great as you will be up against older more mature junior birdmen.
You do get 19 year olds who are mature enough but this is quite rare. Often those who have been head boy or girl at school, although there is not certainty even if this occurs. They are often destined for far more prestigious professions.
Maturity is an important component and most young people are unlikely to develop sufficient of it until at least 21+. University should provide sufficient ‘rounding’, and improve anyone’s chances.