There's no denying that gaming is a huge part of pop culture. Obviously, it wasn't always like it is today: back in the earliest days of the industry, gaming was considered something that was exclusively designed for nerds. While it's true that some still view gaming as such, it's clear that gaming has come a long way since the era of Pac-Man and Donkey Kong.
That being said, gaming is still a niche market when compared to other forms of entertainment. The idea of someone playing games regularly - or becoming a 'gamer' - is still a concept that a lot of people aren't familiar with, regardless of how often they play. In Internet communities, sure, being a gamer is an everyday occurrence - but how often to people outside of said dedicated communities refer to themselves as 'gamers'?
As it turns out, not very often. According to a poll conducted by the Pew Research Lab, roughly half of American adults play video games...and yet, only 10% consider themselves 'gamers.'
The term 'gamer' is just that: a term. It's as simple way for people to broadcast their likes and dislikes without feeling the need to really explain themselves. Obviously, the gaming industry is doing just fine - it's hard to imagine that half of America was playing video games back in the '70s and '80s, and the numbers will likely just get better and better from here. What people call themselves is up to them: as long as they're having fun playing video games, does it really matter what they refer to themselves as?
For more on the study of gaming, check out the full report at the official Pew Research Lab site.