Western Democracy can be under threat once again when former communist countries like Russia, and China, as well as new threats from N Korea of nuclear muscle flexing, not that we can't defend, but by being together, we are stronger, and those countries will think twice before committing suicide if they were to launch first N Attack. we are now very much part of Europe ever since we linked our island with mainland Europe via Euro Tunnel, sure you don't want to cut the umbilical cord and starve ourselves.
However, let us not worry about hostilities from these countries, but if we stay, we could have more say and less interference from EU when they have realised we mean business if we leave, no body is ever happy after a divorce, there will always be some heartache, sure we will miss many things, and of course we are going to restrict benefits to many who are abusing our system of benefits.
There more reasons to stay than to leave, but people are only looking at a very narrow angle - migrant workers.