Why have Lena and Simone gotten away with their activities for so long?

Wouldn't you think that authorities would start to get suspicious of all the disappearances on "zombie island"? Especially that the cat people seemed to target well off tourists that would logically leave quite a paper trail. In reality, you would think it would be much smarter to drain the souls of people with less money and connections...people that nobody would notice or care about their disappearance.