My h was like this for very many years, and probably still is, at heart.I agree that family or personal issues are the reason, although they will often deny this.
My h worked so hard and for so long, whilst I was also working and with five children, that it finally caused a rift between us and resulted in infidelity on his part.
From what I have understood since, this isnt uncommon amongst workaholics. Certainly, I was stunned, as he definitely puts work before people of any type, and anyway he chose a long series of online encounters which wouldnt require him to commit too much of himself, whilst still getting the sexual/attention thrill, and at a time of day to suit him.
Interestingly, the major crisis which resulted when I found out, and which for me was something of a last straw, resulted in him making some radical change to his life, and now he is more likely (a year later) to stop at six or six thirty and make time for his relationship, on the basis of use it or lose it.
Personally, I wouldnt advise chosing a workaholic for a life partner, as they so often have extra issues longer term, and are sufficiently damaged by their backgrounds to be less of a support to their partner than is ideal for true intimacy to be sustained long term.