I could really give a rat's arse why they come here. They are illegals who broke our laws by coming. Period. It's for the governments of the illegals to figure out why they came, and what to do with them when we send them back. You sound liberal with your wanting to figure things out. We have laws to make figuring some things out very easy!
You sound liberal with your refusal to investigate cause and effect. Respond to the effect, ignore what causes it.
Send them back, yes, but we will be wasting our time sending a lot of people back, most likely, the same people over and over again, unless we work to create real change.