Obviously if they win and the offsetting loss were larger than the standard deduction it would make sense to itemize.

My only experience with this was a $1,500 tournament (non-poker) win which I got me a 1099 for $1,500 which I could not offset

To be honest with you, if I had a poker win I would not declare it on my taxes (unless it was reported by the casino). But that is purely hypothetical (TO ANY LURKING IRS AGENTS __ I AM REALLY REALLY BAD AT POKER AND I HAVE NEVER EVEN WON A SINGLE PENNY) ---- And that would never be my advice to a client.