That is if they are a professional gambler. It makes sense to practice using real money because that is more challenging than practicing using a demo version of the game. If you aren't a pro gambler, I don't think gambling can contribute on improving your skill.
There is a study that proves that engaging in gambling activity can sharpen a person's mind and thus can improve brain-related skills. It was discussed in
one of the threads here in the gambling discussion
But before we can sharpen our minds and improve our skills, we can lose a lot due to the many factors of the temptation to spend more money on gambling. This we must realize and although we want to improve our skills, we must also remember that gambling can cause us to become addicted. I think many other activities can also help sharpen the mind and improve skills, not playing gambling, so we will not have problems later.