The average man on the street who wants to leave sees leaving as a way of reducing the flow of inbound immigrants who come equipped with cultures and customs that are difficult to integrate. It's that simple in their minds. They don't give a monkey's about how leaving the EU may affect big businesses like O2 or M&S, air travel or the Square Mile.
The average man cares more about the social/cultural changes, wages and the increased pressure on infrastructure/services brought about the recent waves of mass immigration.
The migration crisis hasn't abated and it'll only become worse as time passes - number of new migrants into Europe have already hit 100k this year. A lot of people who want leave see leaving as a way of curbing the side effects of this growing problem.
For the average leaver it's purely about reducing immigration and nothing else.