In Robinson Crusoe, Daniel Defoe doesn't care to elaborate much on the relationship between the title character and his parents. There are a number of reasons for this.
First and foremost, Defoe wants to emphasize Crusoe's rugged individualism. Here is a man from a relatively modest background who wants to break free from the rigid class structure of seventeenth-century England and make his own way in the world.
Somewhat inevitably, this entails ignoring his parents' advice to follow the middle path of life. Instead, Crusoe will do his own thing, setting out on the high seas in order to seek his fortune.
Though it's all too common these days for sons and daughters to pay absolutely no attention whatsoever to their parents' wishes, this was a relatively rare phenomenon in Crusoe's day. Parents, especially the father, were expected to rule their children with a rod of iron. To disobey one's parents was seen as nothing short of scandalous, an affront to the natural order of things as set down by God.
In not caring to elaborate on the relationship between Crusoe and his parents, Defoe is emphasizing Crusoe's estrangement from God, from whom his mother and father ultimately derive their parental authority.
In due course, this estrangement will come to have damaging consequences for Crusoe. But for now, as he gets ready to embark upon a life of adventure, he's not really thinking about the dangers. And so he pays no heed either to his parents or the filial duty he owes them.