@Paul *********
The point is, possession of a license does not imply an ability to drive well, or even to drive at all, especially if you can just pay an official to pass, or they pass you anyway if you "nearly passed".
There are many good reasons not to be unlicensed and I think most Thais aren't so dumb as to avoid applying for one, except for poor rural dwellers who only own a scooter and never really go anywhere (ie they never leave their village or district).