Ask someone who DIDN"T use them...
You'll have to ask someone that didn't use them, as even though I'm not sure they are 100% necissary, I also had them when there weren't any other options...
There are a lot of places that don't take credit/debit cards in never-never land. Cash is still king in rural areas. You'd be surprised... Personally I liked not having to worry about finding the ATM or the extra walking to get to one...
Now that i think more about it, I am almost definitely going to use them again. We never had to think about where our money was coming from, which means what we used was a good system! :)
Gravity Man