Clearly it's all a matter of degree.
An absent father is not good for the child. And there are different kinds of "absent" fathers: Fathers who just disappear, fathers who disappear but support the mother / child financially, fathers who come back regularly or irregularly. Fathers who die. Fathers who are in jail (guilty or innocently), or away for their job for long times.
A father dependent on alcohol isn't good for the child, but there are various degrees how strong the dependency is, and how it affects everyday life. One person may be a total wreck all week, another may disappear once a month for a weekend and may never be visibly drunk at home. And of course a person can drink too much without being alcohol dependent (yet).
An abusive father (and abusive and alcohol dependent may be statistically correlated, but any individual may be one but not the other) isn't good for the child, but again there is a huge range from mostly harmless to absolutely harmful behaviour.
So you need to weigh up, depending on an individual case, what causes more and what causes less damage. Every individual case will be different.
In practice, no law can force a father to stay with the child. And in cases where the law forces the father to leave the child, it is obviously assumed that the father being present is so harmful that an absent father cannot possibly be worse.
The interesting case would be a father asking himself whether it is better for the children if he leaves. You think your father should have asked himself that question. On the other hand, being an adult now, you could ask yourself whether and how much damage would have been caused to the father by leaving. Did having a wife and children keep him from going completely under?