Free play won't give you a challenge. You play without any worries since no money will be lost.
Test what you learned by risking your money. Just give it a try and if you think you are not capable yet to challenge a real game, you can back again at your practice and training session by playing on free money.
Have you ever made a lot of money and made a casino helpless with this game?
Is there a story already with this case for real?
Low chance to happened or maybe close to zero but if it really happened, maybe only a few gamblers are capable to do it.