Online casinos I think have contributed to the growth in numbers of people betting online games. The retired professor never really get to gamble all his life until he retired and was exposed to social media and then the casinos advertised on in.
Upon his browsing, he came across an ad about winning some cash. But I agree to us being human which he is probably been thinking of gambling when he was younger and in his current situation online gambling is the very option.
The fact that now almost anyone who has a smartphone can go to an online casino certainly increases the number of players, and it even seems to me that there are many more casinos now than there used to be, maybe this is the main reason, because there are many more players. Maybe this professor would not want to go to a casino because he did not want to be seen there, but now he can start playing anonymously and not worry about anything.