If the statistic is true and authentic then the reason could be as a result of betting in cryptos is a daily transaction whereas in trading a trader withdrawal might be on weekly or monthly basis depending on the trader's choice likewise miners however the above mentioned statistics of betting cannot paint cryptos in a bad light because those betting transactions are carried out legitimately.
If those numbers are true then the reason why trading transactions are not number one is because when you deposit your money in an exchange and you begin to trade all movements you make with your coins are not done on the blockchain but in their database and a transaction is not made until you get your coins out of the exchange, so if you are a day trader and you make 100 different trades and then you get your money out of the exchange only one transaction will be registered on the blockchain.