Chargebacks exist for fraud and non-delivery: a stolen card, goods that never arrived. A gambling deposit that you authorised and gambled is neither, and card schemes treat the service as delivered when the wagers were placed. Disputing such a deposit as fraud is itself a false statement to the bank, and operators respond to chargebacks by closing the account, banning the player, and pursuing the debt.
The chargeback questions worth asking run the other way: deposits on a stolen card, or transactions from a self-excluded account that the operator should have blocked, are legitimate disputes, and regulators have sanctioned operators for failures on both. Where gambling itself is the problem, the working tools are deposit limits and self-exclusion, not the payments system.
Why it matters
Chargeback firms advertise recovery of gambling losses to people at their most desperate, usually for a fee and rarely with success. Knowing what the mechanism is for prevents paying twice for the same loss.
Related