Probably going after those once a year travellers who never garner a large balance of miles before they expire. For them it makes sense (barely). However for us with enough miles to be redeemed, it's pointless.
At least China Airlines has decent service in the air/ground. It's just thier FFP that bites. On EVA, English on their website is so unclear that I can't even understand the meaning of the page.
To a local 5 USD is 150 NT, which is an hour salary for many Taiwanese!