Certainly that needs to be addressed. But border security and immigration reform refer to different, though obviously related, matters. The southern border is not secure (I'm not certain that any of our borders are). Drugs and illegal immigrants do enter the country from there. A physical barrier isn't total solution because it doesn't address the immigration debacles you mentioned above, but it does help to limit border crossing and the scope of the surveillance necessary to address illegal entry. Tunnels are, compared to crossing a river or walking over an imaginary line, expensive. They require more effort, technology and money. We'll never make the border totally secure, but making the cost of crossing it more expensive will at least increase our border security.