Unfortunately, its the power of the internet.
Send 1,000 emails and if you get a 0.1% hit rate you've got a victim. Send 100,000 and you could get 100 victims.
The thing that fascinates me is the range of quality ... some look very good, yet others are so bad, I laugh myself silly - I'm just waiting for one that displays a url like: "scammingwebsite.com.cn" - I've had a few come real close!