Well, that is because it _is_ an enclave in which speaking French is the majority "normal" and surrounded by provinces in which speaking English is normal.
If Quebec did not enforce language laws then English would end up driving out French except for decorative, heritage functions.
The result of the language laws is that we have a part of North America strongly bound in to not just a significant part of the EU but also to Vietnam, large parts of Africa and the rest of la Francophonie. Not a bad thing at all.
With the advent of the internet and the new generations of Quebecers being mostly online, as well as being generally more educated in english than their parents through standard school curriculum, I expect this to change in the next hundred years. I’m 28 years old now and I welcome this future, being isolated has a great price.