In all honesty I think you're being a bit binary about this. No, laws are not repealed simply because lots of people break them. Conversely, though, they are unlikely to be repealed if nobody has a problem with them - what would be the point of all that expense legalising something that nobody wants to do anyway? Bringing about a change in the law requires (among other things) the ability to demonstrate that the change would have popular public support: campaigns are part of this, and being able to point to people who are already ignoring it is another part. And the experience of other countries and so on, etc etc. You can't simply say it's A or B or C: there are 600-odd people voting for or against the change and they each have their own reasons which are probably some combination of the above in varying proportions