One does not live by bread alone (Matthew 4:4).Much of modern politics is premised on the rejection of that famous sentence of Jesus. It is the economy and economic issues - the famous Reagan question, "Are you better off now than you were four years ago?" - that typically tend to dominate modern democratic politics. That is certainly the premise of the "Remain" campaign in the United Kingdom, which seeks to scare voters into choosing to stay in the EU for fear of the the possibly negative economic consequences of leaving. And they may be right. On the other hand, of course, no one really knows what would happen to Britain's and Europe's economies if the UK exited the EU, because it hasn't happened before. And anyway predicting the future is always notoriously dubious.
If, on the other hand, the "Leave" side wins, it will not be primarily because of economic arguments. It will be because - as Jesus said - "One does not live by bread alone." (Needless to say, Jesus obviously had something more important than national politics in mind, but that is another issue.) The point is that there are, it turns out, other things, less tangible (but no less real) things, that matter to people besides the economy. Such things include a sense of belonging and meaning, which in the modern world are most likely to be found in one's relationship with one's national state. In the modern world, it has been the national state that alone has been able to provide people with any serious sense of civic meaning and group belonging. True, part of that has been due to the fact that, at least until recently (prior to contemporary "globalization"), it was the national state that was able to provide a certain level of economic security and well being as well. But no one should underestimate the force of a shared history and a shared outlook on the world, rooted in a common experience
Of course, there are parts of the world where national states are more notional than real. In the Middle East (and much of Africa) many state borders are artificial at best and do not correspond significantly to any truly shared history or communal experience. It is no accident that those are places where religion plays a greater role in defining people's identities. In the West, on the contrary, national states have been long established, while religion as a significant source of group identity has been in decline.
One can debate the economic merits of the EU. but as a symbol-creating community, capable of uniting people with common experience, common memories, common aspirations, and common loyalties, it has been a notorious failure. Even if the "Remain" campaign wins in the UK, the foundational failures of the EU remain exposed for increasingly disgruntled Europeans to recognize.
Economic issues naturally tend to dominate political decision-making when the foundations are secure. Within a community of shared history and shared aspirations, when there is a consensus on the foundations of society, then economic questions will naturally dominate political discourse. But when the very foundations of society are shaken, when they have been thrown into doubt, when consensus about who we are as a people and what we ultimately care about has been destroyed or severely diminished, then those concerns inevitably dominate. The mere fact that a referendum on the UK's continued EU membership was needed is ample testimony to the reality that people care about who they are as a community at least as much as they care about the economy. If the "Leave" side wins, that will just be further confirmation that such things really are more important and that really one does not live by bread alone.