Well, I absolutely agree with all that you just said. But still, knowing what sentences the judge can dole out is important. The problem with mob-rousing stuff such as apostasy... or Frankenstein-monster raising, or being Black, or a Hugonot, or an adulterer, depending on context... is that you could easily be subjected to "mob justice", and there would be impunity for your murderers: Pontius Piwatus keeps his hands cwean, and evewyone is happy (the dead can't compwain).

Many countries have laws which are widely broken and selectively enforced,

For example lots of Iranian people drink, have casual sex and there's a surprisingly active gay scene. The laws are only ever enforced when they need an easy way to crack down on protesters. That doesn't indicate any sincere belief on the part of the regime in the moral seriousness of those crimes, any more than if someone you disliked sent the health inspectors round.

Edit Better example: If you looked only at law you would think the vast majority of the American public massively disapproved of recreational drug use. Whereas they are widely tolerated, socially accepted in many contexts and the laws are enforced selectively.