If someone can carry out the responsibilities of modern life; ie., pay their rent/house payment, eat, support themselves and family, pay bills, socialize - essentially achieve all the goals that keep them healthy, why should gaming be shameful or irresponsible?

As Arcticwind points out, baseball, football, traditional "games" and "sports" are exempt from this projected sense of responsibility. Computer and video gaming are "new" leisure activities. They suffer from this the same stigmas that affected novels, music (even Mozart was considered vulgar in his time), theatre, movies, and even the aformentioned sports.

People can be responsible without the need to project that responsibility to others. They can be adults without having to prove to others that they are. Being 18 or 21 or 41 does not make one responsible or adult. We come to those things in our own selves, not at the behest of others or time. Some cultures do have rites of passage, I doubt that abstinence from computer gaming is a prerequisite of any of them.

Thousands of years ago, the exiled Highborne landed on the shores of Lordaeron and founded the enchanted kingdom of Quel'Thalas. These high elves, as they called themselves, created a fount of vast, magical energies within the heart of their land - the Sunwell. Over time, they grew dependant on the Sunwell's unstable energies - regardless of the bitter lessons they'd learned in ages past.
During the Third War, the villainous Prince Arthas invaded Quel'Thalas and reduced the once-mighty realm to rubble and ashes. His undead army decimated nearly ninety percent of the high elven population. In addition, he used the Sunwell's energies to resurrect Kel'thuzad - a powerful undead Lich - thereby fouling the Sunwell's mystical waters. The few elven survivors, realizing that they had been cut off from the source of their arcane power, grew increasingly volatile and desperate