"If you really were offered refuge in France why would you risk crossing a dangerous stretch of freezing water in an inflatable overcrowded dingy to get here??"

There must be some pretty major reasons. Two that I'd imagine is language and friends/family already here.

If you'd travelled all that way, risking death, with your brother, for example, would you say "ah well, I'll never see him again and I can just stay here where I can't communicate with anyone and am completely alone for the rest of my life"

Or "I've already got this far, what's one more obstacle?"