To take a clear look at the discussion again, in gambling financial needs comes first before addiction, so if there is a rise in the population of gamblers, they didn't start to gamble because they want to become addicted but most of them actually started gambling because they had interest of making money from it but they became addicted on the process.
It is as you said it. To be addicted to gambling comes
after the need to get/ find money. This need drives people to gamble and yes, some of them become addicted. So regarding the OP's question about the reason for the rise in gambling, the answer is the bad economy that we all facing and live in. If people had their basic needs covered, then this rise wouldn't exist.