On a purely practical level - the UK voted for Brexit - a simple in/out decision. However, it is not a simple matter to manage the process of leaving, with all the things that need to be decided and negotiated.
Do we want that process done by just the PM and her Cabinet, or do we want all of our MPs to be involved?
For the person who, early in the thread, said this was the start of the death of democracy, I would argue that it is the exact opposite. Democracy is expressed in the UK via our elected Members of Parliament - so if ordinary MPs had been excluded from the brexit process, that would have been u democratic.
Do we really want to set a precedent where decisions as important and far-reaching as those surrounding Brexit can be taken by executive order, with our democratically elected representatives having no say? I don't.