There is another consideration. Just putting it as plainly as I can, our culture contains many tempting alternatives to Catholicism, that go under the name of "Christian", and there's probably not a single one of them that would turn away a disaffected Catholic. Simply put, these alternatives present a generally easier vision of salvation (Orthodoxy would be an exception to this, and I'm not including them in this observation), people listen to them, it "sounds good", and if the Catholic Church would go full-court-press on concepts of judgment and damnation for those who die in mortal sin, we would probably lose even more people than we already do. Add to this, the mortal sins to which human nature inclines most strongly are those of the flesh. Many Christian confessions at least tacitly believe that these are "no big deal", and entirely deny the sinfulness of some of them, such as contraception. Add to this, many Catholics are no longer fearful of losing their salvation by leaving the Church, indeed, some of the more severe Christian confessions explicitly tell them that they will be damned if they stay in it (think Jack Chick comic books).
Long story short, if the Church pressed the matter, and highlighted God's justice, people would just leave. Truly the tail wagging the dog.