They are testing for only one reason. So they don't have to pay any cast members extra hours to sit and pass out wristbands. Also you are correct in that some cast members don't even bother to check to see if guests are wearing wrist bands. Plus this helps out the cast members who want to go on the rides where their friends are working. But it all comes down to not having to pay LABOUR COSTS. Here is a tip for you. Since they have been letting guests get their sodas refilled at the Electric Umbrella in EPCOT this will be happening at all the quick service sit down locations in the near future to again save on LABOUR COSTS.