The problem is that everybody is afraid of what other people will say if they “settle” for a working boy. It’s assumed that there must be something “wrong” with the girl, so people will talk, wonder “what’s wrong with the family,” etc. Also, they may worry that it will harm the younger girls’ shidduchim.
The real problem in all this is the parents and their need to keep up appearances. Supposedly the parents do the selecting because the young people themselves aren’t mature enough to choose wisely. Looking over the current scene, I think in many cases the parents are less mature than the kids.