Online casinos have a weakness that may never really be strengthened.  That weakness is the social element of online casinos.  While most online casinos have chat room features that allow players to communicate with each other it is not the same level of social interaction as found at brick and mortar casinos.

Brick and mortar casinos offer more than just gambling, that may be the reason online casinos have managed to fair better financially.  But when people come to brick and mortar casinos it is rarely just for a night of gambling, even though they may refer to it as such.  Until online casinos a night of gambling usually meant a night of drinking and eating with friends, flirting with the opposite sex, and maybe even catching a show, all while hitting slot machines and table games.

Casinos are places of pure entertainment.  The average casino resort offers hotel rooms, entertainment venues, shops, restaurants, and crowds and interesting people all usually there in search of the same type of good time.  Heck in some of the Las Vegas mega casinos people can find themselves on amusement park rides.  While online casinos have kept their focus on offering games to make money, many brick and mortar casinos have gotten into the heads in beds business of the travel destination business.  

So while, yes, online casinos do allow people to reach out to one another, there is no real way, with current technology that they can rival the social environment offered by brick and mortar casinos since they were first built.