What sparked the "gaming movement" that is active today?
Basically, the digitisation of our culture as a whole directly affected our entertainment. Zoom out of gaming for a bit, and look at people's general lifestyles.
Nerdrant comin' up~Laptops, netbooks, smartphones, GPS in cars, facebook as the medium of choice for contact, humans have begun to live a life completely immersed/dependent on technology. Information used to be something we had to go out of the way to obtain, such as through books and newspapers, but now we're drowning in it. This oversaturation of information and being conditioned with daily networking is part of our daily lives.
Back to gaming. Games, and playing, have been part of natural human behaviour since forever. I'm sure we all know this. Before they were contained in digital form, the most popular and accessible games were in the form of sports, board games, playing cards, etc. So I guess naturally, if you liked, played, and were good at popular games like sports, you were 'cool'.
But as technology developed and more people used computers for their convenience, things like gaming evolved with it. Naturally, it also became wider and more varied to encompass the various needs of its ever expanding audience. Games are entertainment, kids might want it more, but adults need it as well. I still remember when I'd grab a computer just to play solitaire, then later pinball, because I wanted to have fun but no one else was around to play with. Things like Angry Birds is built around this same concept, add to the fact that it's portable, simple and you don't need to go out of your way to buy a 'console' for it, and you have a very popular and widely accepted game. And you have to admit, it's much more entertaining than solitaire.
Things get accepted by communities as soon as they become popular or normal. That's just how people are. Technology is popular and normal nowadays because it's easy to access and convenient. What's harder? Calling your mates out for a football game or organising a round of CSS over IM? They're both fun~ People prefer one because it's easier. Of course that doesn't mean other games have become obsolete, since there are experiences you can only get from them, but it's helped with the popularity of video gaming a lot.
So has the commercialisation of games. But commercialisation goes for everything nowadays because of, you know, oversaturation of information. People have realised that digital entertainment has money in it, so they sell it to as much people as they can. Games for really young kids, games for older people, games for your grandparents. It's a little sad though to see kids being patronised and reducing them only being able play 'easy', 'nice' games. Kids are fine with the themes of life/death/blood/whatever, they're not stupid. And they can figure out difficult puzzles and timing just fine. But that's a rant for somewhere else.
But hey, tl;dr: Because games are fun bro \o/