Credit cards are aren’t as widely accepted anymore, thanks to the US Department of Justice. Because of this, most online casino players now use alternate deposit methods such as NETeller, Firepay, 900Pay, etc.
If you learn about NETeller and then possibly write a tutorial for your visitors — i.e. teach them how to use NETeller to make a deposit — then you might see an increase in your conversions. NETeller is accepted at virtually every online casino.